Usually accessory structures are limited to 30% of the rear yard and must be accessory to the primary structure.

I just bought a SFH in DC and plan to convert the basement to an accessory apartment.

If not, maybe target one with an in law/ accessory apartment (for the income)...Boom you are landlord... 

I have my own inventory of furniture and accessories that I use for vacant spaces.

No need to be an, accessory after the fact, because of your tenants illegal entrepreneurial pursuits.  

I'm 39 and live in Yorktown Heights, NY where I own a house with an accessory cottage which I rent out.

You also cannot do a Cashout Refinance in Texas through FHA, which would allow a singlewide.You may be able to accomplish the majority of what you're looking to do through a Construction loan (pay off land loan, fence, generator, well house, potentially even some renovations to the mobile homes if listed as Accessory Dwelling Units), but you mentioned not being ready to make the move on new construction on the property yet.It may also work as an FHA 203k Renovation loan, but these can be extremely cumbersome and expensive to close.

Although maybe not a comfortable thing maybe also consider buying a home with an accessory unit or living in one unit of a multifamily.

I’m weighing a bunch of different options right now and need feedback from the community :)I purchased a home about a year ago with a legal accessory apartment in Long Island NY.

We may have discussed some of these previously but I'll list my ideas of your type of situation.Review the city/town's zoning by-laws to understand the allowable use for accessory dwelling unit (ADU).