Some buyers can use an offer letter mortgage to qualify for a home loan before starting their new job. Here's how offer letter loans work.Provide proof of job offer. An employment letter is a crucial document you need to secure a home loan. Read about how to write a winning employment letter for mortgage. As a firsttime home buyer, you may not have the twoyear job history for mortgage that lenders look for. Here's how you can still qualify. However, if those aren't available, they will likely depend on an offer letter as described above. There are a few banks and building societies that will approve a mortgage with a job offer letter so long as it starts in the next three months. An offer letter loan is any type of mortgage that receives lender approval based on a job offer letter.