My wife's siblings have built 2 house on this land as there own houses they are living in The property is a total of 15 acre and each siblings got a portion of the property.

Windows would be my next check-point (less than R1) and then wall insulation: I would not be surprised if they have no insulation inside, but you can do blow-in, which only requires a small hole.A home looses heat in two ways: heat conduction (which you can slow down with insulation) and drafts, which in old houses is usually the biggest culprit.

I still have that house and it's bought me at least 5 other properties.

What do you want to be , a house flipper , or a landlord ?   

I do think house hacking and small multifamily are the best plays at the moment. 

The house looked like it hadn’t been loved since 2004 (its build year).

Both houses need a new roof that will cost 15k. 

While I haven’t chosen a specific niche yet, I’m leaning toward purchasing a multi-unit apartment where my 20-year-old son could live and help manage while we rent out the other units—essentially a form of house-hacking.So far, I’ve connected with a few real estate agents and gained MLS access, which has been a great starting point.

If in the future they try to buy a house, the lender may require it to be paid but that's a long shot. 

I guess the only thing giving me hesitation is that it looks like housing prices are at all time highs even after adjusting for inflation:https://fred.stlouisfed.org/se...Housing affordability is worse today than it was at the bubble peak in 2006 if you believe Case Shiller data.