The issue is how are you paid?
If you are full time, salaried and receive a W2, you are fine because lenders can verify your income easily.
If you are part time, hourly and receive a W2, you will need a letter from your employer that your income will continue for the next 3 years and that your hours will not be reduced.
If you are an independent contractor, self employed and receive a 1099, lenders need 2 years of employment because your income cannot be verified and lenders will average out an annual income from the 2 years. You will also need 2 years tax returns.
In addition to employment /income, lenders will pull your credit and verify credit score and history, savings / investments and debt to income ratio. You will need cash for a down payment + cash to pay closing costs.
Age is not a factor to getting a mortgage loan. It's against the law.