Question Regarding using lease for funding

[Michael Oliver]

Long story short-ish:

I have a current mortgage and my DTI is too high, but the thing is an amazing STR. Would do 5k a year easily. Has a flavor for all seasons.

But I have to live there.  Im trying to move out so it can make that but I'm just throwing money away living there. 

I have 325k left of my VA Loan. I found a duplex for 318k but can't get approved in the lending side. Many people have talked about getting a lease for the STR. My question is does that lease need to be valid? Or can it be fabricated? Will the lender investigate it? The STR will produce way more, but it's not accepted. I feel like I may be cheating the system by using a fake lease, but the fake lease would just be 1/2 of what the real income would produce.