We build year round in MN. You get used to the cold. Snow is just another obstacle and many winters lately has not been an issue. We pretty much do anything to a house at any time of year. Really subzero days its not advised to work outside but 20F and above is fine.
Not to rain on your parade but:
If you are flipping, most of that is interior work anyway. Now, getting into that business may be hard as many localities have people that snap this stuff up faster than you can find it. I've done a few in southern MN and pretty much can say I wish I would not have spent the time and money on it. Small returns for a huge amount of time let alone the costs of materials.
If you are also dealing with the trades to do the work, your profit margin is going to be close to 0. Electrical, plumbing etc would need to be done by trades folks as it's not legal to do this yourself if you are reselling (in MN). You can certainly do this for yourself if you are living in the house, but it won't take long for them to find you out if doing all this on your own and the end purpose is selling.
If you are dealing with realtors to buy and then sell your projects, that's who is making money, not the guy with the hammer. Having the realtor license and a broker to work with would certainly help on the profit end.
Anyway, good luck!