If you can find an IFR C150, and you fit comfortably in it's smaller seats, then by all means buy one. By IFR, I mean it needs to have the radios necessary to get your IFR training, and then have the inspections required to make it legal for IFR flight. A lot of C150s won't have enough nav equipment to get you through the Instrument rating.
Insurance is going to be a bit steep until you have around 200 hrs and the instrument rating. It should get pretty reasonable afterwards. I pay $800/yr for an IFR C172 insured for around $50K. If you can afford a hanger where you're at, then I recommend you hangar it. If you leave it tied down outside, it's going to need an interior and paint in about 5-7 years. (At least in Texas it would). That's if a hail storm or microburst doesn't destroy it first. If you get a good one, I'd budget around $100/mo for maint and annuals. Could run more or a bit less depending on the condition of the aircraft and the price of maint where you are. My C172 has cost around $4K per year for fixed costs, insurance, hangar, and maint./annuals.