@Jasmine Cotes , I still think your best bet is reaching out to mortgage brokers and spent some time loan shopping -- it's a great way to learn too. My husband and I looked into doing something similar to what you want to do, except we were moving from a condo to a duplex and moving to another city because of work. Because we wanted to keep the condo, the first mortgage broker we talked to would only offer us investment loans requiring 20-25% and 6 months PITI reserves for both our old condo and the new house plus we needed funds for closing. In other words to finance a modest $150k duplex, we needed to have close to $70k in the bank. This despite of having excellent credit, solid jobs, and some money saved -- alas not $70k.
We kept saving and then we talked to a few other mortgage brokers including a couple who specialized in FHA 203K loans. While brokers cannot bend underwriting requirements, your broker should be able to help you understand what you need to do to meet qualifications and find a lender/loan that better matches your situation.
Among these other brokers and lenders (do talk to your local bank!) we found loans with better terms including 203k loans As OOs, they required 3.5% down, PITI reserves for both properties between 3-6 months, and included the possibility of rolling closing costs into the loan. These loans involved PMI, but that was balanced by a lower interest rate and a much lower cash-in amount than the investment loan. Mind you, we still needed a substantial amount to pull this off (its Jersey after all), but it sure was a far cry from $70k.
Again, reach out to mortgage brokers and explain your situation clearly, and whatever you do, I'd strongly advise you refrain from using any language that even hints at breaking the rules or finding loopholes or "work-arounds." In fact, if you come across a broker that promises to fit you into loan for which you don't legitimately qualify, RUN! Somebody who thinks they can cheat the feds and the banks won't think twice about cheating you.