Walked in with equity; however, I also added storage racks and electrical updates.

You should spend the extra 10-15 hours per week reaching out and networking with General Partners of multi-family, self-storage, and industrial syndications while educating yourself on how syndications work. 

I would like thoughts on how to finance (we would need approx. 200k) building a duplex (a barniminium with half storage half and 2 -2 bedroom apartments).

The house is in extremely similar condition to ours (25-30k rehab) when we started but has a storage building, covered back porch, and little more yard space.

He can’t afford storage either.

Rather than prattle on about this I will point you too this article I wrote on this topic recently:  https://www.biggerpockets.com/blog/investing-in-self-storage-why-cap-rates-dont-matter-that-much#:~:text=If%20you%20don't%20have,be%20unable%20to%20refinance%20it.

Make it a master suite or something like that.It looks structurally safe, they intend that Attic to be storage so weight shouldn't be a problem. 

All he would have to do is rent a self storage locker and put the motorcycles in there as well as his endless collection of tools.When they moved in I was there and didnt see any of this hoard. 

RV parks, mobile home parks, and self storage all are great options.

The use of open fires, fire pits, fireworks, charcoal burning grills, gasfired grills, or other devices shall comply all relevant federal, state,and/or local laws.I am curious, can I just list it on AirBnB and other sites not VRBO?