I’m also in DFW and interested in doing a hybrid of owner/builder after the mechanical phase.

If they don't need an "official" floor plan, there is a free app where you walk around the room with your mobile device pointed at where the floor and wall meets.

2) Are Vendor Mechanic's Liens extinguished at tax sale? 

They setup to assist clients from all over the US and have great online/mobile banking system so you don't even need to go to a branch for your banking needs.

Closeups of all mechanicals (hot water heater, furnace, etc.)

Mobile homes and such? 

The mechanics of it.  

Mobile home parks can provide consistent income, and if you manage it well, they could become a significant source of cash flow.

You may wish to confirm that the new 401k provider has experience with the particular investments in which you intend to invest your retirement funds as you very likely will have questions in terms of the mechanics (e.g. how do you invest in real estate, etc.).3.

@Frank Rolfe's Mobile Home Park Bootcamp is the gold standard!