If you pay for a new one or repair, then you will have a new or repaired water heater. I guess you can always remove it if it doesn't close.
Very few lenders will approve a buyer when certain criteria arent met with the home.
Actually, once the repair is made, it has to stay with the property and can't be removed if the deal isn't approved.
If it were a personal item, like a range that is plugged in, than that would be a different case. But fixtures and repairs can't be removed or 'undone' for lack of a better word.
Try to negotiate with the seller for reimbursement of the expense if you can't close on the property. Otherwise, you are out the $$ for the repair.
Not if the lender or the appraiser has made it a condition in your loan.
If your loan is not conditioned on the repair, than yes, you can repair it after closing.
Ask the lender if they can escrow the repair costs to be completed post closing. Done quite often.
You will incur a post closing inspection fee payable at closing.... But worth it to be protected.