A roommate can offset costs, reducing the $600/month shortfall.

"what is your experience living with room mates?"

Would it  be possible to get an additional roommate where you and your boyfriend live?

In my almost 20 years of doing Subject 2's and working with other investors in almost every State in the US, in the very few instances the Due on Sale is called it is because if the inexperience of the Investor in not knowing how the transaction is to be done, (not closing with a Title Company or Attorney, not doing the Insurance correctly)Most of all, (not communicating with the seller) Bank calls the Seller to offer them Life Insurance or some other service, and the seller tells them, "I don't own that house any longer, some guy took that house from me and put some renter in it"If you dig into any investor that tells you they had a property or a friend of their brother in laws Collage roommate that had the Due on Sale clause called, you will most likely find that the investor screwed up somewhere.This is why Education and knowledge is needed on any Real Estate transaction.I get calls almost everyday from someone who screwed up on a Subject 2 and is asking to be bailed out, many times they do not want to pay for help, and things just get worse.If you know how to make the Bank Comfortable with the transaction, all is good.Last year I had a couple of hedge fund managers call me asking how they can offer their under preforming loans to Investors to by Subject 2, wow what a great deal, I could call Pace and he would have buyers the same day for a 1,000 homes, but the legal aspect of this would hold the Hedge fund liable so we could not do a deal.

This property is a shared unit so we don't want a locksmith to change locks, then the roommate is locked out.

A 3 bedroom house with two roommates would bring in around $1,400/month, and a home in the high $200k's with 3-5% down would have a mortgage pmt around $2k/month.

If one roommate bails, that isn't your problem.

If you're ok with roommates and generating some leases, ground rules, and interviewing folks before they move in, you really can't go wrong with house hacking.

@Wei Zhao,Consider house hacking with roommates in a SFH if you can.

Also, it sounds like you are in a great time of life to rent to roommates - I don't think you would regret figuring out a way to do some sort of house hack like that right now!