You'll need to research & interview with different brokerages as you'll be required to affiliate with one before you can begin actively selling.

I have tax/legal affiliates who are doing this all day every day.

Not real estimating or underwriting but a start, the numbers smell like a decent range https://www.dwellito.com/adu-cost-calculator I am not affiliated 

I have a degree in game and web design have tried Affiliate Marketing , Building and running my own eCommerce website buying and selling of Amazon and Ebay .

Affiliate sites are great for that kind of stuff too, I've used FlexOffers in the past for rental cars, groceries, doordash, etc.Another option I've seen a lot of chatter about lately is TheHost.co - they have a network of different offers around the US and only make money on the processing, no cost to sign up.

I don't have any affiliation with them.

Title companies affiliated with ALTA all follow the same rules which allow QCs into LLCs wholly owned by the named insured. 

I'm assuming you are going to sell the property to the annuity company or an affiliated company on installment sale and then they will immediately turn around and sell to your buyer. 

But someone in your family has to have military affiliations.

Pacific Manufactured Homes (no affiliation) has a show room near me that they had 8 models to view.