It could be a flat rate ($25) or percentage

Anyone experienced have a system that they use to determine this number by a percentage or some such?

I'm in the education phase and one thing that I was wondering was how do I pay back a hard money lender and a private lender who put all the money down how do I calculate their percentage into my analysis somebody could break this down for me or lead me to where I could find this I would be grateful.

Has anyone ever purchased a percentage of ownership in a rental property?  

The Solo 401(k) also has the advantage of being more favorable for real estate investments using debt-financing such as a mortgage - as the 401(k) is exempted from a small tax called UDFI that an IRA would pay on the percentage of income derived from the borrowed money.So, as you continue your research and get feedback here on BP, think about what type of program will best suit you needs and be sure to ask questions along that line.

Will it be a percentage fee?

Because you are going to be utilizing a large percentage of a large line of credit, it could affect their ability to get credit if you are maxing out that line.

At the end of the rehab, refinance and give him a percentage on top of what he would have charged.

A percentage of that was calculated as part of my income so my personal W2 income isn't considered my only source of income.

Every percentage point will have significant implications.