With a homebuilt you can choose if to do DIY maintenance or give it to a company.
If you don’t want to use a company, you have to either be technically good, or find somebody (or go into a syndicate with) who will do the work.
And for sure owning a homebuilt turboprop needs way more expertise than owning say an RV 
But somebody buying a homebuilt TP ought to know that… and he always has the “company” option.
