Do these dollars make sense? (Are my numbers adding up?)

[Ben Kirchner]

I've quickly learned this forum has a great amount of knowledge. I'm hoping someone good with numbers can be so kind to review my figures to assist me with my current situation. So I'm looking into purchasing a new house as a new primary residence, then rent on my current primary residence (and only property). I'm trying to crunch the numbers to figure out what my search criteria should be for this new residence. Below are all the numbers and details.

I have bought one home, which is my primary residence.

Paid: $140,000 (in September 2013)

Loan: 15 year FHA 3.5% interest rate

Current equity: $29,000 (Down payment was around $13,000. $16,000 from mortgage payments)

Mortgage + HOA: $1295 ($1175 + $119 HOA)

Payoff date: September 2028

By taking out a 15 yr loan, I sill wonder if that was a good move or bad move. It has certainly allowed me to build up some equity in the 2.5 years that I've owned the property. However, other townhomes in the community rent for about $1150, so if I rented my place out, I would need to put money out of my own pocket into the mortgage. I'll own it outright in 12 years, however.

Assuming buying an investment property would need 20% down payment, it would take me into next year to save that. I was considering buying a new property as my new primary residence this year, then rent it out and buy a new primary residence next year, then repeat that process for maybe.. 5 years? Ideally hoping to expand my investment portfolio, and hopefully make a little cash flow from the rents I would be receiving from the properties.

What I'm struggling with right now, is crunching the numbers to find what I would need out of my next primary residence to make for a better cashflow situation than I currently have going for me. I currently rent a room in my residence, which covers part of the mortgage. I would need to find a property where I would be paying less out of pocket than what I'm paying now.

My current situation:

Mortgage+HOA: $1295

Roomate rent: $$555

Out of pocket expense: $740

If I rent this property for $1150, that still leaves me paying $145 out of pocket. As a very rough estimate of other expenses and vacancy factor, let's say $250?

If this year I purchase a home as my primary residence for 5% down payment, I would basically need to find myself in a situation where I'm paying <=$490 per month for the property. Are my numbers correct? Or am I missing something big? The latter is certainly a big possibility. I sincerely appreciate anyone willing to help me analyze this situation.

Ben