Most lenders require that you have at least one year of employment history for a part-time job to include income from the part-time job when you apply for mortgage. This guidelines is determined by Fannie Mae, the organization that sets mortgage qualification guidelines followed by almost all lenders. I have included the specific lender guideline below that addresses part-time employment for borrowers.
As you can see below, two years of work history is actually preferred but lenders can include income from part-time work with at least a one year of work history as long as "positive factor" are involved. Examples of positive factors include a higher credit score and stability of income for both your full-time and part-time employment. It is also helpful to provide the lender a letter from your part-time employer stating that the job is permanent, as opposed to temporary, and verifying your income and job stability.
"Verification of a minimum history of two years of uninterrupted secondary employment income is recommended. However, income that has been received for a shorter period of time (no less than 12 months) may be considered as acceptable income, as long as there are positive factors to reasonably offset the shorter income history."
While I think it may be challenging for you to find a lender that permits a shorter employment history for a part-time job, I recommend that you contact multiple lenders to understand how they would handle your unique situation. You can compare lenders in your area by clicking INTEREST RATES
If you cannot find a lender that allows a short employment history for a part-time job, you could consider applying for the mortgage without including the part-time job or waiting until you have worked at the part-time job at least a year. You can use our Mortgage Qualification Calculator to determine what size mortgage you can afford based on various monthly gross income and debt expense scenarios to understand if you qualify for the mortgage amount you want with or without the income from the part-time job.