#1 you don’t need a sewing machine to shorten jersey t-shirts. You can trim them, they keep a rolled edge reasonably well.
#2 what Jaileen said regarding lessons. It seems to be a popular thing. In fact a local fabric store for quilters closed down, only to reopen as a sewing machine store - and they are promoting their products via lessons!
#3 what LJP wrote. I started with a basic Singer and sewed tons of things on it (kids clothes, Holloween costumes, curtains, patchwork). Since I was serious about my sewing, I upgraded to the best mechanical sewing machine (a Pfaff) that I could afford. It’s never let me down. I can do some of the servicing myself, but bring it in to a pro for a tune up regularly just the same.
My top 3 prized possessions used to be my piano, my road bike, and my sewing machine. I donated the piano to a retirement home a couple of years ago (finger issues), and sold the bicycle this summer. I still have the sewing machine and it gets used regularly.