What is an acceptable/reasonable interest rate to split with a hard money lender? 

I doubt a good agent will allow the seller to accept your offer if you don't have a solid financial status.

I believe that there are auctioneers who will accept a flat fee regardless if the property sells but you must do your own marketing.

My first offer ever on a property, a large commercial property at that, and it gets accepted!

@Melissa Gittens I watched the market on this house until it dropped into a range the offer would get accepted.  

So, if I wanted to sell for $100,000 but   later accepted $50,000, you're thinking you're lender would accept your negotiation skills as a 50% down payment?

Then determine what their acceptance criteria is.

If the deal could be reduced to a loan, if you could decide what an acceptable rate of return (rather than a share of potential profits) it would be easy.

The investors have been very difficult to work with from the very beginning with grinding us down on our prices to a very very slim profit margin (almost making the job not worth taking but we got so far in deep we accepted any way).We originally asked for a 50% deposit prior to work starting as we have never worked with this particular investor and then we would collect the remaining balance once work has been completed.They had two other bids but decided to go with us because of the quality of our work as showcased in the portfolio we presented to them.Well, they managed to get us down to 25% of deposit (initially they asked for 10%).

In real estate, the path of least resistance is not the correct path to take, it is very structured by laws, regulations and accepted practices.