The STR deal could be the best option if I understand your situation correctly, except I would probably do this as a cash-out refi and just use the combination of booking history + AirDNA projected income to qualify (if not operated as a STR for a year).

It is a combination of reviews, pricing, amenities, quality of photos/listing, and CTR (click-through rate). 

Combined with an additional pledge on the newly purchase 6-plex and your lender is in a much better position than the 100% financing. 

The answer is a combination of knowing the numbers, your projections of those numbers in the future, and your confidence in your ability to do the analysis. 

Contribution - some want to provide good housing options.Most will have a combination of all these factors.QUESTIONS.What type of cash flow are you looking to generate? 

Mobile is ranked 7th in the U.S. for least stressful city, and 25th as the best city in the U.S. for Millennials to live.Employment Information -- The top providing employers of Mobile are The University of South Alabama, Infirmary Health Systems, and Austal, who combined provide over 14,000 jobs.- The Mobile Aeroplex brings in another big economic industry which is Aviation.

Make sure your listing is SEO optimized with the right keywords to attract more renters—many property management companies can help with this, along with tenant screening and payment management.

There are two separate issues here: one is combining your personal and business banking which can complicate filing your taxes and is generally frowned upon.

Quote from @Seo Hui Han: A HELOC and a Home Equity Loan are the same thing.I have an excellent residential mortgage broker who can help you with this, he's based in Orange County. 

Main thing for you is: - Have both you and your buddy talk to the same lender and get pre-approved to understand down payment options and what your combined budget would be- Decide how you want title held (joint tenancy or tenants in common) - do a google search on this to see which option is best for you guys- START SHOPPING!