This sounds glib but I'm quite serious:
Just buy and use this book: https://www.amazon.com/Strength-Training-Anatomy-Workout-Bodyweight/dp/1450400957
It's as good as an introductory text gets. One thing I'll say is that if you're literally starting from scratch when it comes to fitness of any kind, it won't be a bad idea to get a pair of running shoes (you can lift weights in them too as long as they're not those r-tarted Hoka One One boots) and do a 45 minute jog maybe twice per week. It'll help you diagnose where weak or overworked areas on your body, help you stay losing weight, and give you a chance to show off that new bod, bud
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edit: dear god I originally posted a zoom link from my chat with school friends last night, how tf old am I
This is kinda hood but if you can afford it, this works better than a doorframe mounted bar and will last a lifetime (Chinesium is alright when designs are simple)
Get some gymnastics rings to hang from it, and you've pretty much got all the equipment for back workouts you'll ever need.
A cheap pair of dip bars later (https://www.amazon.com/dp/B07PH9PP85/ref=redir_mobile_desktop?_encoding=UTF8&aaxitk=82d3bc7e902b441749818c6a7edb3aa7&hsa_cr_id=8558718970201&pd_rd_plhdr=t&pd_rd_r=97811fc2-4c61-4bf4-8d1f-3ec82c776c06&pd_rd_w=JC8bf&pd_rd_wg=...), and you'll have all the equipment you need to completely jacked with bodyweight alone if you have the discipline. All of this can fit in a few square feet.
Bring a bar with you. Depends on if you're able to accommodate that.
These kind of bars could travel pretty easily and wouldn't mess up any doorway that you're staying at, most likely.
I use one of these, combined with rings. Can do a huge amount of exercises with that, and rings wouldn't be hard to travel with, either.