Alex is right and next time don't make promises based on what another person (in your case, the handyman) promises.

You are trying to get his general thoughts on his being open to it or more closed off based on bad experiences in the past.If he seems neutral to positive you could bring up you are thinking of bringing in a partner on a deal and start talking about the property and details.

Any recommendations for reasonable lawyers that could help me structure the agreement with my uncle to ensure all our bases are covered, it's optimized for taxes, and that he eventually gets the income he is due over time for selling the property to me.As you can see, I have many questions and I know this is a huge project, but I'm committed and I know it's an amazing opportunity. 

If I use percentages, than that would change based on the selling price of the apartment.

I've noticed in my research that rent price varies based on if and what utilities are included.

When doing your calculations for ROI, do you base it on the actual amount you have in it or on the amount that the property is worth(ARV, etc)?

If your looking to make an educated guess base your value on the homes that have sol and then add you best guess as to value of the additional land.  

I am also based out of South Jersey.

Now there are obviously many other ways to find deals and if you want a more detailed approach feel free to PM me and I will give you a more specific ideas based on your more detailed picture of what you want to do. 

Based on these lessons decide on one niche and attack it and get a property.