Hard money lending criteria can be anything the lender feels comfortable originating with a particular borrower. Generally, institutional loans are lower interest (12-14%) and higher closing costs (2-5 points, appraisal, survey, plus additional fees) while private money is higher interest (14-16%) and lower closing costs (1-2 points, no appraisal, survey, or junk fees).
In addition to higher closing costs, the institutional lender will require more documentation on the property, usually an appraisal, and the loan amount will be based on a pre-determined loan-to-value ratio. Many institutional lenders will also charge a prepayment penalty if the loan is paid off prematurely. The payments may be interest only or fully amortizing up to 15 years. Some lenders may escrow funds for repairs.
Private lending criteria is best described as "anything goes." Each lender has his or her own lending criteria. Flexibility is a real advantage in dealing with a private lender. It's their money; they make the rules. And with time, the lending is based more and more on a personal relationship with the borrower. Some private lenders will do 100% of the purchase price. Others will require a loan-to-value ratio based on current value or rehabbed value. Sometimes a prepayment penalty will be charged. Costs will range from nothing up to 5 points. Usually the term will be interest only up to 60 months.