how to break in to just about anywhere for dirt cheap

This guide is basically just to show you that you can break into places like gun stores with cheap things like microwaves and booze. Usually to break into a place with reinforced doors and concrete walls you need a sledgehammer, but if a fire appears on the SAME TILE as a wall or door then it will either vanish if it's a door or become a burnt wall that you can climb through. Anyway let's get to the good stuff!

Just about anything can burn but sometimes it can't be burned from the side you are on. This is a little complex to put into writing but I will try to explain it in a way that makes sense. Each tile has stuff on it such as floors, furniture, walls, fences, doors, roofs, and other various buildings. If a fire breaks out on a tile then it will burn ANYTHING except for non-flammable floors and roofs (I am unsure about items but corpses burn so I assume items burn too). You should keep note that you CANNOT BURN CERTAIN WALLS DUE TO THEM BEING PLACED ON AN INSIDE TILE AND NOT ON AN OUTSIDE TILE. An example of this would be a building surrounded by sand with carpeted floor on the inside of the building. you want the walls to be placed on the sand because you can burn the sand from the outside, if the walls were on the carpet then you would have to start a fire from the inside to burn the wall. To check if something is burnable then click the floor under the wall on the side you wanna burn from and see if the debug info mentions stuff about the wall or just the floor, if it mentions tags like 'Thumpable=' then that probably is the tile you gotta burn. though relying on debug tools is not very reliable because they most likely will be disabled after b42 unstable is no longer an unstable build. A (probably) better way to check is to place an item on the tile you are gonna burn and then click the 'pick up' button (the ui button that looks like a dresser with an up arrow above it) and hover over it, the little preview window that appears will show whatever is on the tile (including walls). All of this is pretty confusing so here is a crappy MS paint image of where you want your fire to be to burn through something.

Microwaves can be found just about anywhere, can be picked up for free and without any strength needed, and can start a fire at the cost of needing power and any metal item. The only issue is that microwave don't seem to be hot enough to burn a large enough hole in a wall to climb through, like they burn the wall but holding E to climb through doesn't work. Burning doors on the other hand is entirely possible and really easy, heck you can even burn through the despised reinforced doors that tend to keep you from getting that big bounty of guns you want. It is as simple as placing the microwave on the SAME TILE as the reinforced door, then all you gotta do is put any metallic item inside the microwave and turn all the dials to max and turn it on. After you turn on the microwave it will burst into flames and destroy just about any object on that tile on a molecular level until they vanish... except for walls which just get a tan and sit there uncaring.

Sometimes you wanna break into somewhere that has those metal bar things on the same tile as a reinforced door that turn into walls when burnt. Stendo's has all of it's doors barred up so microwaves won't work on it... So maybe you should have a drink of whisky at the bar that's like 3 feet away from Stendo's to forget about your sorrows. Wait a second! Whisky (among a few other alcohols and gasoline) can be made into molotovs for really cheap. Other alcohols that cannot be made into molotovs can be poured out and filled up with gasoline (except beer bottle because they are too small to make molies with them). now all you gotta do is grab a lighter to put in you secondary hand and put a molotov in your main hand and huck it at a wall THAT CAN BE BURNED FROM THE OUTSIDE. After you throw the molotov run in the opposite direction to get away from it before it breaks so you don't get splashed with fire, and then just wait for the fire to disappear. Now you should hopefully have at least one wall that had a hot enough fire on it that it has a big enough hole burnt into it that can be climbed through by holding E (by default)t, if you were unlucky and got no way from one molotov then try another and another until you burn into the building or make the difficult decision to give up and go somewhere else or run out of molotovs. It should be noted that trying to burn a wall inside a building is a bad idea especially if you are in a small enclosed space, mostly because throwing something that splashes flaming liquid all over a room that will probably boil you or pull some bull crap mechanic that saps all the air out of the room or something (disclaimer: I have no clue if fire inside a building will cause any effect to air quality other than increasing the room temperature). If you wanna burn into a room from the inside then use a microwave and burn through a door or cut your loses and just molotov it from outside.

The most expensive part of molotovs is the bottle but if you have the artisan talent then you start with the recipe for most glass recipes and can easily make glass cups until you unlock the bottle recipe. If you need a bunch of molten glass but don't have sand to melt then go to a nearby town and start smashing all the window and grabbing the glass shards (with gloves on) and melt those down. to actually start glassmaking you need a simple furnace, a small crucible (it can't be a normal sized crucible), tongs, pliers, glass blowing pipe, and a crafting surface.
Don't forget that microwaves need power to start a fire. I know it might be stupid that I have to tell you this but some people might just straight up forget that microwaves cannot be relied upon when the power goes out.
Molotovs cannot be used unless you also have a lighter or disposable lighter in you secondary slot.
Molotovs take about 2 minutes to make which is surprisingly long given how you are basically just stuff a rag in a bottle.
Dirty rags and and denim strips can be used in the molotov recipe but sterile ones seemingly cannot.
Things like firebombs, pipe bombs, and aerosol bombs also start fires, but I suggest keeping them for hoards unless you are in a pinch and really need to get through a wall or door.
firebombs don't need a lighter (I don't actually know if it needs a lighter but the wiki doesn't mention it needing one) and are generally cheaper, use them instead if you have the recipe unlocked.
You should ALWAYS keep something to extinguish any possible fires that spread such as water or fire extinguishers.
Do not start fires near grass unless there is no better way to get in and/or you have plenty of stuff to extinguish a spreading fire.
Clear out any nearby zombies to avoid them walking into a fire and burning everything you know and love. Seriously zombies take very little burn damage and spread fires everywhere including to other zombies, and it only takes a little bit of grass to slowly burn the entire town away until it reaches your base.
It's always a good idea to keep a few molotovs and a lighter in your car just in case you find a place with good loot that you want to burn your way into.

Hope you learned something and that something can help you survive. Most of this guide is written like garbage because I don't tend to write guides. If you find out something cool to add to this guide or need help or found an error in this guide then leave a comment. Anyway I've gotta go drink some water and you need to go get to committing some productive arson. Good luck out there survivor!