What interest rate do you assume sellers have on their mortgage?

[Jose Falconett]

For purposes of an investor doing there due diligence and also for situation where a seller has no clue what they owe, interest rate, monthly payment amount etc.

Since mortgage notes recorded in the public records does not show interest rate only length of mortgage and its principle, what interest rates do you assume a seller would have and how can I learn how to assume this properly?

I've had investors tell me if it was 2010 then likely around 5%. Can anybody instruct me or give me some kind of trend for interest rates!? THANKS