How will the existing income from the property influence the amount I can borrow? 

This doesn't come cheap--these folks were making high six to seven figures depending on volume.We focused on lending to professional real estate investors--so our customers were frequent repeat borrowers. 

I imagine the whole process is simpler but can anyone tell me how different it is when you don't borrow the rehab costs?

Offering flexibility has allowed my borrowers to swing into deals they would not have been able to do previously.You’ve made a great point about the importance of being easy to work with and fostering strong relationships with lenders.

One said the 2nd mortgage has to be assumable and the other said it did not.VA issued Circular #26­24­17 back in August to try and clear up the issue:Assumability: If the secondary borrowing is not assumable, the holder of the VA guaranteed loan should counsel the assumer that this may restrict their ability to sell the property to another creditworthy assumer through an assumption in the future.The lender currently servicing the loan still can decide whether or not they'll allow the 2nd.You could do seller financing for the gap and then refinance just that amount with a Home Equity Loan or Line of Credit at some point down the road. 

HUD 4000.1 (I believe) is the latest HUD handbook and it goes over all requirements for originating the loan, including but not limited to occupancy requirements and exemptions.FHA occupancy : "At least one Borrower must occupy the Property within 60 Days of signing the security instrument and intend to continue occupancy for at least one year."

to simplify, here's what i would do: don't borrow private money, or partner, until you have a track record. 

This could also hurt my debt ratios if I go to borrow on another investment somewhere like my plans for the STR.  

If you conclude the leverage is so good that everyone comes out ahead that's fine but if you are only able to originate hard money debt that may be viewed as a red flag by investors who will question your experience and borrowing strength.

Many real estate investors opt for a fix-and-flip loan because they’re relatively easy to obtain: no personal income verification (no DTI requirements), and you can often borrow up to 90% of the purchase price and 100% of the rehab costs.