Lots of stuff missing in this. Big one to be doing without good cash reserves, but the numbers look pretty good.
First off, what are your taxes on this thing? That's always a concern up north. I barely factor them in in Atlanta and have a house in Cleveland that I paid $105k for and found out when I refi'd it the taxes were $8k/yr. I was like "huh?" The taxes were as much as a mortgage would be on that much money, crazy.
So you've really got two things to look at here. First is how much equity to you create by doing that much work. Basically, what can you buy it for, how much does it cost to fix, what can you sell it for?
Then, you have a cash flow model that says OK how much will I have in this thing and how much will it kick off in income? That's when you need to compare income to expenses and money cost and figure out the cap rate, etc.
In between the two you've gotta figure out what your costs are to get from one to the other, they are two very different analyses. The roof is not a future expense, it needs to be in your rehab. You're just asking for trouble letting that one slide.
10 1 beds you should be able to do for $10k-15k each assuming they're fairly small and you can get some bulk pricing and such. Then the roof and violations. $250k is probably right in that market, but thats a guess, I've never tried to fix anything in Mass, I just know that it costs more than the markets I'm in.
$100k in income on a $600k investment works all day long, your long term prospects are great. Just gotta make sure you can get it full and have the cash to get there. You'll lose some tenants when you start construction. People don't like change, even if its better for them. Just gotta factor in some extra lost rent when planning cash. Also, my experience with 1 bedrooms is the tenants suck, you want to screen them well.
Good luck, sounds like a winner to me.