Hello,
Since I have been dealing with this issue myself and preparing for the worst with my i-130; I would like to say that "cash" isnt' always the king.
One of the vj members was denied visa at Delhi on the basis that the USC didn't stay 1 month in India prior to getting the marriage certificate, I guess they got the marriage certificate within a week's time or something like that and the official requirement for let it be an Indian by birth or a foreigner is 1 month 10 days to be exact.
I do realise that not every case is being scrutinised like this and every case is different, but then it's better to do it proper way than being sorry later on. And also with what all I have read, it feels like you can do things giving out cash in some parts of India but not every part.
So may be asking your fiance to contact any of the local lawyers of her/his district will be a good idea.
Also are you a OCI? Just make sure your fiancé go to any local family based lawyer or registrar office and clear up things beforehand.
Oh another thing which I have seen is, if you have less time and your fiancé doesn't live in any municipal area rather his/her domicile comes under any panchayat raj, then a certificate given by the panchayat holds as much value as registering, since panchayat is part of the Indian government.
Please do more searches and see what all options are available for you and your fiancé and move according to that.
Best wishes for your future