Hello,
as others have already said, if you can pay for the property from your equity, then the stress/pressure is off when it comes to building the house. Then you can still look around in peace. Worst case is everything is too expensive, and you're stuck with the property. You could also finance 20k, for example, through a small loan and pay it back quickly. I don't know how high your savings rate is.
However, I can't shake the feeling that you have fixated on this under 350k (including the property). What will you do if it costs more? What does your house bank say about the project, up to what amount would they finance you? These are fundamental questions you should clarify beforehand. Your net fluctuates, probably due to commission payments. Every bank also calculates different amounts. 3500 net then only counts as 2200 net in the household budget calculation.
My personal tip. This "I know everyone and everyone helps everyone." I also come from a rural area. The problem with that is, everything that costs nothing, costs nothing. That means you rely on acquaintances, might have to somehow pay them after all, and coordinate it yourself. And you can forget about any guarantees/warranties.