This is a single family home and was originally a primary residence before turning it into an long-term rental.Some strategies I'm considering to grow my portfolio are using a HELOC/1039 tax exchange to purchase a second investment property/multi-family property or refinancing my current investment property into a conventional loan to utilize another FHA loan for a primary residence (with the idea of eventually turning that into another long-term rental).I currently have a 7% interest rate, and am considering refinancing in the coming months if/when the rates drop.

Why not 5% down conventional, seems like that works with the available cash and closes this at $100K. 

It sounds like you are running into hurdles with conventional financing. 

Conventional Mortgage 5% down and 4% interest rate.

One of the good things about DSCR Lenders is that the guidelines and programs are different and not cookie-cutter 100% equivalent like conventional lenders that all must mirror the GSEs, etc.Most DSCR Lenders will have similar rates and terms and generally similar processes - so generally what will make the "best" one is the best one for your needs - I would focus on any specialties or niches - like short term rentals, if you do multifamily or mixed use, BRRRR Method or focus in on a specific market - find someone who specializes and has a good track record in that niche or area

However, you could try pushing again with the 900k (cash, DSCR, conventional etc) plus whatever terms/contingencies you want to add.

Purchase price: $257,150 Cash invested: $12,000 House hacking Duplex purchased using Conventional 5% down loan.

I don't qualify for any more conventional loans so now I need to go the commercial route.

Ideally I will be using a 5% conventional loan and will be funding the DP+ closing costs myself.

Keep reading, listening to podcasts, and learning from others' experiences to refine your strategies.Consider Your Financing Options: Explore different financing options, such as conventional loans, hard money loans, or even partnering with other investors, to find what works best for your situation.I'd love to connect and share more insights as you embark on this journey.