There's lots of tax planning on this and I would suggest to take a professional opinion on how to structure a transaction in a way that you can make it into capital gain tax or reduce self-employment tax.

Have run Facebook ads (not very good ROI for me, but do get friend requests from unknown men and women who think I'm attractive and stupid), and often drive for dollars...as in, at least once a week I take a different way to where I'm going. 3 times in 6 years I drove by a FSBO (for sale by owner) sign and it resulted in a successful transaction. 

The borrowing against a 401k could potentially come in handy for a fix-and-flip or BRRR type transactions as you can quickly return the funds to the 401k.

My property manager uses AppFolio, which is fine for transaction level detail and a few dashboards.

And by the way, in transactions I would always be the seller, so to me what you said is very favorable.

They are properties circulated to long lists of unsophisticated buyers and if you are the highest offer you’ve likely outbid a bunch of prospective buyers who underestimated their improvement costs or overestimated their ARV while most likely  proceeding without the ability to perform normal transaction diligence.

But everyone is looking to 1 call close on real estate transactions. 

I need to have a way to roughly calculate how much I might earn in a land transaction. 

If we had gone through with the transaction and somehow obtained right of first refusal written notice, would the seller be legally held accountable without us forcing litigation?

But, excel is totally fine in the beginning (in addition to your PM software to capture transactions outside of the properties).We use QuickBooks Online exclusively for all of our REI Clients.