Don't lose any sleep over it, call them and explain the circumstances.
Best wishes to your husband!
West USA Realy
First and second home loans are for when you plan to occupy the home (not rent it out) and are financed at a lower rate than an investment home. You should not have an issue, you can call your lender to confirm. You may also call your insurance to reflect your occupancy intentions,
WEST USA REALTY
TOP 1% Selling Agent
I replied to your question on the other site, and the answer is "No". You will be using it for a purpose which is LESS risky to your lender than you originally intended, so you are fine. If you were going the other way (primary to second or investment/rental) then you might have an issue.
In response to Brad's comment "you are likely being charged a higher interest rate for the 2nd home"--I do not believe that is the case. The interest rates are pretty much the same for primary and second homes; the differences usually come in the form of having to put more money down, not being able to borrower as much money on a cash-out; requiring higher credit scores, etc., vs. higher interest rates.
Good luck. Sorry to hear about your husband's diagnosis...