Even though they are renovated, they have to be pretty old in Richardson, maybe 70s vintage, so I would want to know who rehabbed them and what did they actually do....like new electrical and plumbing...any foundation work?

I'd include:Development and design.PermitsStreet and walks.Driveways and foundations (for garage and house without basement)Utilities stabs for sewer, water, gas, power, cable And any other factor I'm forgetting.Thank you.

I know someone who had major structural issues with their foundation, got it fixed and was told by the lawyers that they didn't need to disclose it when they sold the house (they did disclose it).

Could I hire someone to do the foundation, utility connections and framing, then do the rest myself to save money?

Our foundation is shared with the house attached to us. 

I poured the foundation myself using quickset cement ($30 plus my time).

I understand that notes is a business best learned by doing, but I am trying to lay a good foundation of knowledge as a starting point.To date, I have read these books:"Invest like a Bank" by Beaux Blast" Little Green Book of Note Investing" by Fred Moskowitz"Real Estate Note Investing" by Dave Van Horn"Note Investing Made Easier" by Martin Saenz"Invest in Debt" by Jimmy Napier"Profiting from Non-performing Mortgage Notes" by Amed HazelI welcome any thoughts or recommendations that the group may have.   

Few things with MH that need to be assured is "Double wide" which you covered, On a permanent foundation/concrete slab, Not on axles/remove, Not moved from another property or living location, and built after June 1976 (Some investors require within 25 years). 

I am a "Foundation" Big Dog which is the lowest level that anyone can join at.

It's a favorable rate, and given the equity you have in your property, you have a good foundation for securing additional funding without compromising this rate.Considering your property is now an investment, and you're looking into financing options for updates, a VA loan could still be a viable path for you, even in your current situation.