We, many years ago bought a chainsaw, axe and splitting chisels etc. We do it all by ourselves, the old saying burning wood keeps you warm twice is so true. Also the whole family get involved, I and my eldest cut and split it and the youngest transport it and my wife stacks it.
If you are burning wood to save money, buying wood is no good. If you are burning wood just for a bit of extra heat or visual purposes then ok to buy it.
Often go for a walk in the woods and come back with fallen branch.
I also tow my trailer quite a bit. There are some nice laybys ( I wont name the roads on here ) that are worth pulling into a couple of times a year. Load up the fallen branches and off.
I would like to add I have never cut down a tree on property I don't own or have the owners permission to be on, but the local woods are Forestry Commision and walking off with the odd fallen branch may or may not be against the rules/laws, I don't know but have never been challenged..
Burning wood can be very cheap with just just a little effort.
Any wood will burn nicely if aged enough. Pine is horrible when green. But store it long enough and it burns fine. My favourite is apple wood.