Hello,

You can find JEE ADVANCE sample papers and preparation modules for a very cheap price or for free from aspirants who have appeared for JEE ADVANCE. Also you may find such materials from a used books shop or anywhere convenient of that sort. Also instead of offline coaching you can search for online videos on YouTube for jee advance preparation. You will get enough content online. Coaching would cost a lot and since you belong to a poor background you may not be able to afford coaching centres. However many coaching centres provide scholarships too based on your performance in a test that they would conduct.