Tl;Dr: the title of the post

I'm going to start HRT in a couple weeks and I need to dress business casual at the minimum at work. I'm not a big fan of dresses and skirts and I don't have a lot of money to buy a ton of new clothes with, so what are some good brands or styles of pants that will keep fitting as my proportions change? I don't want to wear sweats to work until I know what size to buy pants in, but I also have no idea what extent of changes to expect from HRT since no one in my immediate family has transitioned.

Am I overthinking this? I just want to avoid spending a fortune on pants in the next year.