I've been thinking about buying a Cessna 150, any idea what an owner can
expect annual expenses to be.

I.e., Hangar, maintenance, inspections, etc.?

Depends on the part of the country. Around DFW, hangars are $200-250, open,
covered T hangars are 100-150, open tie-downs usually about $85. On a 150,
annuals run around $350-500 just for the inspection part - that's without
any other parts/labor.