Traditional mortgages aren't for construction sites.

As someone who used to work in my dad's construction business in NY I can tell you that when you have three layers of roofing and a foot an half of snow sitting for weeks on a roof on an older house, weight can become a big problem. 

The idea is to consider the single-wide as the "primary" unit (that's how it's being sold) and apply for a construction loan to finance both the primary unit (the man home) and the future ADU. 

New homes are sold before the construction is even finished. 

I know Richmond has tons of little pockets and it seems like there’s always new construction

For example, I did not check as many references as I should have for the contractor, I did not know a lot about his construction background or past successful projects.

Their husband works in sales in the construction industry so well connected to the builders in the region.

Add-a-lvls, bump outs, new construction, open floor plans, etc... 

I’m self employed and do cabinetry for a living and am savvy with a lot of other construction areas.

For example, if a construction company needed to finance a crane but their bank said no.