With that, if I were the seller, I'd ask for a little more than the current market value of the land.

I started off with 3 houses on a lot and another house two lots down.

I have some experience doing this and I reacted when I heard that 99% of agents don't know what seller financing is. 

There's a specific forum for House Hacking.You'll want to spend some time reading through there as it's a common topic.

These areas have affordable entry points, diverse housing stock, and steady demand.

.- If you're going after a seller finance deal I think once you understand what it will take to get to a finished state its simply a matter of aligning your needs as far as short term cashflow with the current rents/situation, with the net number the seller needs after the refinance.  

Can you buy a house and be within reason of what your current rent? 

Get your CRM up and running and keep in contact with everyone with content about the market, keeping in touch with past clients - just asking them how their house is, let them know that you were thinking of them when you drove past the house,  ask them if they made any improvements, etc.

I'm looking to do a third house hack/BRRRR in the next 2 years.

Purchase price: $120,000 Cash invested: $150,000 Dilapidated house.