If I prepaid online do I still need a credit card , and what if its a credit card that doesnt have much funds on it( less than $50)? Are they going to charge it for a deposit or do they just need it just in case when its returned ?

So i have the mastercard i prepaid with online , will they accept my navy fed credit card if i put money on to it

Yes, they are going to put a hold on some funds your accound may go into the negative.

I think you will need the credit card you paid with just to verify it. Not sure you can use it if you can only charge as much as $50 on it. I'd bet not because I didn't reserve online and for some reason they charged me more on my rental. Good car, just more expensive than I'd expected