Yes - the Multifamily DSCR Loan option is a strong option here - not sure if you've seen this BiggerPockets article on Multifamily DSCR (versus traditional MF loans) but sharing here in case it helps - https://www.biggerpockets.com/blog/multifamily-dscr-loansIs the property now fully leased out?

IF he sold with seller using traditional bank money, he would likely owe a 25% tax on that gain having to count the whole 100K that year in his income.

I've also thought about biting the bullet and installing a concrete driveway so regardless of what floor I have I don't have to worry about as much mud getting tracked through the house by a future tenant.

You may want to look into forming a captive insurance company, which acts as a supplement to traditional insurance.

I’m sure in the following 23 years I would have been able to build up at least a $10M portfolio with a ton of owner financed deals and some traditionally financed properties as well given how inexpensive properties were then where I live.

Traditionally housing loans just look like unsecured debt for banks. 

I think I can make the mud a little clear.

Usually down payments range from 0-30% down when targeting investor buyers.At the end of the day, the point of seller financing is that sellers and buyers are able to form agreements that are generally not possible with traditional financing, so there's a lot of wiggle room to customize.

I am not as familiar with seller financing as I am with traditional and other types, but looking for any knowledge I can find.

A drywall patch, mud and repaint will cost your, say, $300 regardless (I know the size of the hole matters, but your rent doesn't).