I absolutely love my boat and love your enthusiasm and consideration of this lifestyle change however, knowing what I do from my very short period of boat ownership (Predator 60), and being far from what I want to tell you, it has to be a no no. You simply cannot go into buying a boat of this size and class without the correct financial reserves as they will get used no matter what you might believe. As others have said, property is where you put your money if you want a return and boats are where you put your money which you can afford to lose.
I treat my boat like a gambling addiction (it is really), in that I will have some truly fantastic days and some les sso but as sure as eggs are eggs, the house will always win.
Sorry for the negative response but I'd hate for you to lose everything and a 108 Pred has the ability to do that to a man if underfunded.
Another consideration though is if you can find others who would go into it with you on a shared ownership scenario where you are presenting the ability to spend much of your time on the boat caring for it and thus avoiding the fees of external care although that's a big ask of others money.
I just love the fact that you are even considering this.
Lots of clever folks above have given you sensible advice from their perspective, I confess if you need, imho, to start measuring the Boating Experience in terms of profit and loss you are really fecked.
Whilst affordability is everything, introducing financial risk just screws up the greatest fun you'll ever have without a partner ( See ! Ive leant , Im now totally PC )
Have you considered shared ownership?I have arranged this for several owners near Palma Mallorca.You turn up for the weeks you want and only pay a part of the total cost.I arrange everything.Yachtsman , Registered Accountant.Hope the mods don't mind this?
Forgot to ask you who will drive your powerboat.I can call upon the services of a Master Mariner who is Captain of a Cruise Liner when not working with me.