The next letter I got was only from one neighbor (the leader of the pack...) and said I was in violation of deed restrictions since some guests appeared to be "unrelated individuals" and the deed restrictions demand single family use.

Our lender helped with the appraisal process and cash out refinance

LOLOLOLOLOLOLI was going to give you some tips or things to check for in your search but ... nope, after your thought process, I'm not going to waste the time ...Good luck!

I'm currently not a high net worth individual but have 1 investment property.

What resources do you use to do background checks and credit checks on individuals and what are the costs associated with these checks?

Separate out the data in individual columns so you can sort my multiple different fields to be able to compare the lenders. 

And I've also had leases for renters that are in the process of building a home and are looking to rent until construction on their new home is complete. 

My biggest concern is around not understanding the process and costs for purchasing a mobile home, having it shipped and fully setup on an existing lot.

Also because the tax sale process is so messy, even if you do a quiet title action (from #3), you may not be able to get title insurance on the property for at least a year.

If you think building and flipping is going to be a piece of cake, it will not, You need to find land, and all that is associated with building, 6-month process or longer.