How does it hold up as far as legality and also is there a decent market for it out there or more trouble than worth.

I’d really love to fix and flip and buy long term rentals but I just don’t have the cash yet and I understand that hard money lenders are very expensive for new investors.Any tips or legal advice for this area would be very helpful!

If this is from a family member, maybe they will not enforce any due on sale provisions or choose to waive enforcement of any sort of provisions restricting transfers, assumptions, assignments, etc. 

I never heard before of the matter until Friday, when I asked him to get back to me with a buy out offered as he had said 2 weeks prior or I would had to get legal counsel.The question here is: Should I take his buy out offer or continue waiting, when I don't trust him anymore?

Is that legal?

I know I will have to deal with legal to get paperwork situated to guarantee those monthly payments. 

what other legal related things do I need to do?

The restriction is the maximum loan is 50% of the face value up to a maximum of $50k.

Not sure what you need, but check Wisconsin Legal Blank. 

As stated above though, get legal review.