Which are the best colleges with low fee structure in Delhi/NCR to get a bachelor degree like BBA or B.Sc?

You need to check some college websites to get to your final decision. I would suggest you to visit IMS UC Ghaziabad to be preferred in Delhi NCR for pursuing BBA or B.Sc. Check the link here to get an idea of the course as well as fee structure https://www.shiksha.com/college/ims-ghaziabad-universi

jamia millia islamia, ggsipu

All government colleges under Delhi University have very reasonable fees. These colleges offer all types of degrees. You may visit DU website for all details.