In general, the effective interest rate for a patent loan will be in the neighborhood of 12-18%.
The patent loan insurance product has a premium that is paid out of the loan proceeds, as well as due diligence fees and insurance premiums for the required enforcement and defense insurance.
When you include interest that is paid back to a lender, the effective interest rate of the loan will be approximately 12-18%.
Please note that this rate is much lower than angel or venture money, which is typically 50% or more. By taking a loan against the assets you already created, you can get much further without having the negative effects of selling your equity to investors.