All of this depends on your market having demand, of course. 

The main downside is being dependent on the HOA—issues like poor management, rising fees, or unexpected assessments can hurt your investment.

For full time management rates can range from 20-30% of gross revenue depending on the level of services provided.

For example, an ADU is nice for a rental, but not every home buyer wants to pay a premium for an ADU on their property.This would be case by case and property dependent.

LENDBASE has the following feesConventional:1% origination fee$500 doc fee (est)Title Work TBDAppraisal $2000-$3000Environmental $0-$2000 (depending on search) Which all seem pretty normal, but FIRST they require you pay them up front $4,000.00 to start brokering loans, it’s their "non-refundable engagement fee.”Has anyone ever heard of this ever?

I know conventional lending could become an issue depending on the condition of the property.

Depending on the resort the 7/9 bedroom was in, yes, it will generally perform better than a 4 bedroom in any reputable resort, including solara. 

A good manager will handle everything from marketing to maintenance and tenant screening, saving you time and stress.Vendors and LandscapingBuilding a team of dependable vendors—like landscaping companies, contractors, and insurance agents—is critical.

The income of a property manager is dependent on whether you property is filled with tenants as well. 

The local investors will need to know their local real estate and rental markets and depending on the infrastructure the investor has in place or is willing and able to build, that will dictate how much time and effort they would need to contribute.