I have several friends that have closed hundred plus of transactions and they asked the seller when do they want to close.

While I have a Broker license, I've don't do any buy/sell transactions.

The fee should be relatively small compared to the investment in a meaningful direct mail campaign.You may also want to chat with a few title companies about what kind of transactions they'd be comfortable with.

In any case there is no taxable event yet.As far as your brother is concerned, it again depends on the nature of the transaction. 

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.

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.

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. 

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.