Do not just get a bowflex.

Fitness, like anything you want to master, has to be properly researched and taken seriously. However, it doesn't have to be prohibitive unless your fitness goals are particularly challenging.

From your comment, the best thing you could do is befriend someone who is open to showing you the ropes when it comes to fitness. If you have $$, a personal trainer could suffice.

Failing either, proper research. Honestly the LLMs would be better than operating from complete abstraction for building a program that aligns with your goals.