Additionally, if there are any contractors in the Fort Lauderdale area who can provide an estimate or guidance on this type of conversion, I’d really appreciate the connection!

But, they will be in challenging parts of town where realistically you do not want to own property and your long-run returns will under-perform.I'd encourage you to find a balance of sub-market growth, nearby employment, strong income, and only then a good rent-to-value ratio. 

Additionally, his credit is not the best, and he has limited funds for a down payment.Any potential options or solutions that may be available?

My biggest concern is managing additional units and tenants.

Also, you will have additional occupancy tax depending whether you are in the city limits or not.

But this comes with pockets of C/D neighborhoods, and higher potential for headaches;  in addition, appreciation in these zips has probably maxed out for a while.

Additionally, it's a good idea to connect with a Property Manager early on.

I haven't heard of the ability to add additional $250k primaries, but I'll have to dig in to try to learn more about that!  

FHA now allows us to count rental income from an ADU (additional dwelling unit) to help borrowers qualify.

When parents employ their minor child, the child is exempt from Social Security and Medicare (aka FICA) - if under 18.