Analyzing Leveraged Situation to buy Second home, Rent out First

[Ernie Park]

Hi all. I'm having a tough time analyzing a potential situation I find myself in. I owner occupy a condo with mortgage in Cambridge, MA. Great (but very expensive) location close to MIT/Harvard. I recently came across a property similar to mine that is more expensive, but nicer that we could buy and move into leveraging the HELOC from our primary residence, and then rent out our current residence.

For such an expensive buy and hold area such as Cambridge, our primary residence has very strong cash flow (relatively) and I believe would make a good rental property while we move into the newer property while taking advantage of the HELOC to cover most of the down payment. We'd also have the benefit of having an owner occupied mortgage rate at both these residences. I've ran a bunch of numbers and analysis on the side of just renting out my existing property, but am having a tough time putting together everything given this particular situation. Is the fact that I get a nicer home + additional cash flow from the rental + equity in a second home worth some initial cash outlay to buy this new home? I know I didn't provide specific numbers, but I'd appreciate getting pointed to resources with similar situations or formulas. Thanks!