Private Investors are interested in two main things: 1. Return on Investment 2. Level of Risk. My suggestion is to create one or more sample (or actual) Investment Analysis to illustrate how a deal will make a strong investment for this lender. The Investment Analysis should outline the details of the deal: Purchase Price, Necessary Repairs, ARV, Holding Costs, and most importantly, cash needed. Based on the cash needed, what interest rate/ terms are you willing to provide? How much will the investor actually gain by investing with you. Also, what security does the investor gain with his investment? This analysis should include pictures and as much detail as possible. For the repairs, detail out the major stages/ costs of the repairs. For the ARV, show a list of comparable sales and their price per Square Foot.
A professional and thorough investment analysis will help to augment your credibility and make private investors feel more comfortable with you. Even if you don't have an actual deal yet, create a sample analysis to give the investor an idea of how you analyze potential deals. Once you have something, start meeting with investors. Private Investors will let you know if your analysis is sufficient or if additional detail is needed. You can then continue to Tweak and adjust for future meetings.
A general Business Plan can be supplemental material that helps to communicate your overall strategy, marketing plan, neighborhoods of interest, company makeup, etc.