Very few private lenders are interested in loaning their money out for more than 6-12 months. I suggest you gather your funds (wholesaling, rehabbing using short-term money, etc.), then look for partners (meaning you have skin in the game too) on ever longer terms.
Another tactic is to obtain longer term loans from institutions. A very common loan is from a bank. Say 75% LTV on a 15-20 year amortization schedule with a 3-5 year "look-back" - meaning in 3-5 years they can either call the note due or change terms (presumably increase your interest rate).
Private Money is a highly misunderstood part of our business and too complex to do well from reading a book or buying some cheap "program" or "home study course" off the Web. Contact me and I'll chafe some of the direction I've mentored my students with over the last few years that's resulted in them solving their REI funding needs.
Best Regards,
-Greg
The REI Mentor
http://www.reimentor.com