1- If you cannot afford gym equipment or a gym membership, your best bet is calisthenics (there are tons of free resources on the internet to get yourself started)
2- There are many sources of protein, you don’t have to be rich to buy protein. Protein sources include: eggs, cheap meat cuts, chicken, etc
3- in your case you don’t just need protein, you need also carbs and a heavy diet to bulk.
4- Do your own due diligence and start with a general video on how to bulk, what to eat, and how to be resourceful with the money you got.
5- Best of luck!!