Before I try to sell the idea to them I'd like to have the best data I can on potential earnings, upkeep costs, likely occupancy, and other points like that.

If you pay cash, you don't have a payment, but effectively you are giving up an income stream if the cash had been in a bond or ETF and earning you either interest or appreciation. 

Although it isn't some miraculous contract that will hold a buyer hostage, there can be repercussions to you and/or the agent you eventually earn a commission with.

We did out earn them.

You are a high w2 earner, The house is worth 110k today, you are buying from your grandma for 60k in exchange for free rent for life, upside ARV of 200k.The costs of owning the house will help provide tax relief on your high w2 earnings, you are buying a great chunk of equity that will pay off in the future, and you and your grandma are doing each other solids. 

If a wholesaler can still profit while provided “full disclosure” and adhering to the rules and regulations of real estate licensees then they’ve earned their profit.   

Mid thirties couple earning very well (more than 8X rent) with a small pet.

This brings me to now, I've taken this approach and have used my own money in lending, but am also bringing in friends and family to take part in these transactions so they can earn way better returns than with CD's.

Ownership and profit-sharing can be split based on contributions, with you possibly earning equity through sweat equity.

Focus on cashflow and growth, earning money for more down payments on more properties.