A first-time buyer, while qualifying for the mortgage, often needs more cash for closing or to make up the down payment.
Some lending institutions, with this in mind, have loan programs that keep these costs as low as possible, but they usually want the first-time buyer to provide 5% of the purchase price from their own funds, rather than from an alternate source such as a family loan or gift.
Lenders' will usually want to examine your bank records over, at least, the last three months and will want you to explain the source of any large, recent deposits. Gifts or family loans won't be included in figuring your personal investment, so if you have funds of this nature in mind when planning the first-time home purchase, try to secure that money well in advance of shopping for a mortgage.
In the case of a gift, be sure that everyone involved understands that's what it is; if it is a loan, a clearly outlined plan for repayment, in writing, will avoid unpleasant misunderstandings somewhere down the road.