The lender will be looking for two things when addressing a departure residence:
1) Does it make sense that you would be truly moving to the new home. For example, if you live in a 3,000 square foot home in Yorba Linda worth $800,000 and are purchasing a 2BR condo for $200,000, than the underwriter will question if you are really going to live there. If the opposite is true, then clearly there would be no questions -
2) Second items is Buy and Bail - this is when a homeowner will rent their current home and have less than 25-30% equity. In this case the lender will not use the rental income as an offset to the current housing expense. If the Buyer qualifies for both homes, than this wont be an issue.
So, depending on your credit, income and savings, you should be able to buy an owner occupied home with no money down for a VA loan, 3.5% for a FHA or 20% or more to avoid mortgage insurance on a conventional loan. So, not sure what the issue is, yet, seems like it should be pretty straightforward.
The only other issue could be if your lender was qualifying you and you needed to put 25% down to meet the income and debt ratios..
if you want additional information, feel free to contact me at firstname.lastname@example.org