It’s a balancing act of controlling costs while also controlling risk of personal injury to your tenants and property visitors as well as maintaining goodwill with all involved at the properties. 

Obviously tough to give advice based on minimal info and no info on your personal situation.

Low LTV, 30yr fixed @4.5% personal (1)• Investment condo - new const. high end purchased w/1031 (from 20yr quad) in 2019.

So why is the $2,500mnth person paying $250 and the other one paying $350 ??????

Personally, I think I would stack some cash for a year or so while I did this. 

I have personally wanted to build my home on this land for 10 years, as I've always been interested in this.Issue is, I've never done any work with residential development, only smaller land development, about 13 acres, and commercial, all on my own.With the residential development, I'm trying to get a sense of anyone in the space currently and what some ballpark costs might be for infrastructure and how that all works.

Then based on @Michael Baum's suggestion, I think I will have my cleaner and/or maintenance person do monthly/quarterly maintenance like using using enzyme based cleaners, grease fighting drain treatments and hot water flushing. 

I found an auction person, and I see listings online.

I also think most markets won't see anywhere close 6% cap rates (for single family homes which is what I personally invest in).The questions you get to ask are then:Is the extra 4% worth the hassle of management and lack of liquidity.   

Most personal loans I have looked at have terms of 10 years or less.