For the most part, the most common scenario is using them as an accessory dwelling - usually "under the radar".

Do they tear down old homes in mature neighbourhoods  and intensify by building towns or semi-detached dwellings?

Also, if your laborers/contractors require payment immediately or up front, you pay that out of pocket, then submit the invoices for reimbursement.The first thing you should do is make sure the lot is zoned for more than one dwelling unit. 

I was blind-sided with the news that my recently bought two-family home is legally a SINGLE FAMILY dwelling. 

These smaller multifamily dwellings are now often referred to as the missing middle.Atlanta's small multifamily, like many cities, are concentrated in the oldest neighborhoods. 

This would be an owner-occupied dwelling and buyers are in the UK.

In DC and in Montgomery County, it's easy enough to look up the zoning maps to see if an address has the proper zoning for building a multifamily dwelling, but I'm having no luck finding this information for Prince George's county.

The correct policy in Personal Insurance is a Dwelling/Fire. 

Fire, dwelling, liability?

If it's worth it, how do i negotiate knowing the purchase price and the land and dwelling value given by the county?