You should discuss it with the buyers and your lawyer. Normally, 5 business days. If you think two weeks are to0 long, you could counter back.
Generally, the buyers should get financial pre-approval before they put an offer. Otherwise, they would like to buy your house, they probably could not afford it finally. If they like your house, they would like to arrange a home inspection ASAP.
If you signed the purchase agreement sent by their lawyer, your house is conditional sold. You could not pick any other offer. BTW, do not forget to ask a deposit. Normally, 5K-10K.