Co-signor a.k.a. Non-Occupying Co-Borrower (in the language of financing) are a recognized and acceptable form of mortgage pre-approval.
Your Father-in-law will have to qualify for the home along with you and your husband. You all should be aware that his co-sigining on your note can obligate him to make the payments should you and your husband not be able to fulfill the obligation.
Also the mortgage he co-signs on most likely will show up in his credit report and could impact his ability to secure his own future financing.
When shopping for this type of financing you might run into a mortgage provider who wants to charge for the extra work involved with a non-occupant co-borrower. Lenders generally do not charge for this type of underwriting. Any such charges are most likley those imposed by your broker/banker for the extra work involved in processing this type of mortgage.