What a voucher actually is, to a lender
A housing assistance payment contract is a documented, contractual rent stream with a government agency behind most of it. Read plainly that is a stronger evidence of rent than a private lease with a tenant nobody has underwritten.
Lenders do not all read it that way. Some count contract rent in full, some use the lesser of contract and market rent, and some discount it. That variation is the whole story, the tenancy is not the problem, lender selection is.
Why it matters most on small-balance property
On a small-balance rental the gap between rent and payment is thin to begin with, so a lender who discounts voucher rent can turn a working deal into a declined one on that single guideline. The same file at a lender who counts the contract clears.
This is why it is worth establishing early which treatment applies rather than assuming. It is a question you can ask before you spend money on an inspection.
The other small-balance constraint
Many institutional lenders set a minimum loan amount, and voucher rentals often sit below it. A perfectly sound property with a solid contract can be declined purely because the loan is too small to be worth underwriting.
Ask about the floor in the same conversation as the voucher treatment. Those two questions together decide most of these files.
What to send
The address, the contract rent, the market rent if you know it, and the current tax and insurance position. Business purpose is available in nearly every state.
Some programs carry additional state restrictions. Eligibility and terms vary by scenario and by lender guidelines; nothing here is a commitment to lend.