The mechanicals were boiler fed baseboard heat and hot water, and no air conditioning. 

My concern is lack of access to mechanicals, pipes etc.  

Also, develop some policies on breakdown, you don't want to be paying for towing the boat if they run out of gas but you would be responsible for mechanical breakdown.

If I need to get my car fixed I go to a mechanic because I know it's a cost associated with owning a car, etc..

Knowing the mechanics is only one part of the equation.

On a FEMA elevation certificate they document the finished floor elevations, and the lowest elevation of mechanical and electrical equipment.

I think the great thing about them is that there is no forced air, no mechanicals to break down, they don't make noise, they don't blow dust or impurities through the house and when you get out of a shower and stand by a vent you're not blow dried.I've converted a couple with a low pressure fan unit keeping the ducts in place using the large plentum, that way you don't get the blowing effects and it's still quiet.Draw backs, asbestos wrapped ducts, those can be covered to meet code.

That is primarily why I became interested in BP, because I too was unfamiliar with real estate as a mechanism for wealth generation or protection.

The toxins are created as a defense mechanism and allow one type of mold to KILL and overtake another mold's real estate.  

When reviewing your local codes you may find some of the older garages were built right up against the property line.If the garage is down new set backs come into play & trust me it can be an added expense not being able to used the old cement pad.We built ours for $4500 but the doors, electrics & ancillary mechanicals add up.One we are considering now would be built against the home with an addition (it's a Cape) above the garage for a master bath & closet.Have fun.