When applying for a mortgage, can I include the income of a roommate?
No. The only income that will be counted is for people signing on the loan itself, either as the borrower or as a guarantor. If you have a signed lease, your lender may consider the rent specified on the lease as part of your income. To make a stronger case for including that rent, you could provide evidence that the roommate in fact did contribute that or a similar amount to paying rent at your current location for the last year. Given the limited enforceability of leases for shared housing, since its hard for courts to require people to continue living together if either of them wants to call it quits, many lenders will give little weight to such a lease, but if theres a good long track record, you might be able to convince them.