Does anyone know of any other ways to gauge the effectiveness of this plan? 

The Retainer Fee is credited towards whatever they buy from us in the 90 days, so in effect, costs them nothing.Note: we're not doing this to make money, but to avoid the time-wasters.

What financing strategy would be most effective?

If it's on your credit, you are on the hook for it.However, it shouldn't effect the loan process too much, a simple Letter Of Explanation should be able to get the job done with the correct investor. 

From experience, finding a knowledgeable accountant is key for handling taxes effectively, especially when splitting expenses, claiming deductions, and managing depreciation.

When offering incentive such as bonuses you must question the effects of this type of motivation.

Maintaining a financial track record for your project is facilitated by effective budgeting.3.

I completely agree with @Ashish Acharya's points about the cost-effectiveness of a HELOC and the potential credit implications if it’s secured by your primary residence.

Does it still provide effective results?

To newer investors, they may rely on their agents to act as the Chief Investment Officer, effectively thinking the agent will bring them only perfect deals that meet their investment objectives.