House Hacking Deal Calculation Adjustments?

[George Wines]

I am sold on the idea of house hacking. Duplex, Triplex, or 4-plex all sound good to me. It makes sense to me to cut your living expenses even if it lowers the cash-flow from the property. I have looked through many of the house hacking related articles, but I havent seen anybody mention if they make a calculation adjustment for if you are house hacking.

What I was looking for would be something in the rental property calculator that also takes into account the rent you are currently paying before you move into the multi-family you are about to purchase.

For a little background on my situation, I am looking to buy in the Denver area near a light rail station. I work in the tech center, but could change jobs to work downtown in the next year or so fairly easily. A light rail location works for me. 

Currently I am paying $650/month all included to rent a room from a guy who owns the apartment. But, I will be moving into the multi-family unit with my significant other who pays a whopping $1360/month because she lives in her own 1br/1ba. Assuming that utilities will cost about the same for her in the new place and since I dont pay utilities, I would count that as a wash. Overall though, this is ~$2K/month.

In the multi-families in the light rail neighborhoods I am looking in (A class in general), rent is between $1-1.5K/month. So if I were to buy a 4plex with 4-1br/1ba units renting at $1200/month each and I lived in one, I would only collect $3600/month but there is also that $2K/month saved in expenses. Can you add that $2K/month in expenses saved to your total return? (If I didnt explain my idea correctly, let me know and I will try to elaborate or rephrase)

Does this sort of calculation make sense to do if you are house hacking? Or should you always look at a deal as if you were not going to live there?