If you own then you will be sharing your time between learning to fly and learning to maintain an old airplane. Also, renting often is less costly and certainly less financially risky than owning.
If you rent, then you will be at the mercy of the renting schedule for when you can get your training hours. If the airplane isn't available when you are, then your training will be dragged out. This will cost you both time and money.
If you own, then you not only have the airplane available for your training but also so you can learn its systems. The owner of a rental would probably take a dim view to you removing cowlings or inspection plates just to see how things work. Most auto drivers have no clue how a car actually works, but they also can just pull over on the side of the road to call a tow truck if something breaks. A good pilot also knows about the mechanics and can diagnose issues in flight, so as to increase the chances of a good outcome.
There's a spreadsheet that floated around the forum (and is probably still available) that helps calculate the cost of ownership based on hours flown per year (some costs are fixed per year and others are based on number of hours). It factors in setting aside money for eventual overhauls or other repairs.
Plus, they ain't making any more 150s and high wing Cessnas (150/152, 172, 177, 182, 210, etc) are always going to be in demand. A bunch of 150/152s got exported during the 2008 financial crisis and other attrition has taken a toll on the fleet. Prices have continued to go up and I'm not seeing any reason for them to not continue to go up.
