Hey,
It's great that want to become a doctor. This proffesion gives you an opportunity to help others and at the same time,you get to earn respect in the society and let's not get into the monetary aspect of it. A doctor earns a lot!
See,in India,NEET is your pathway to get into the medical colleges across India. So,you need to qualify it.
Since,your background is weak,then you need to start from the scratch. First off,have faith in yourself and don't get disheartened no matter what!
Make a time table and stick to it.
Get yourself enrolled in a coaching institution for they will help you understand the pattern and teach you tricks to ace the exam.
Be thorough with your NCERT Physics,Chemistry and Biology.
Practice previous years paper. Work on building concepts.
For detailed information about the preparation follow the link given below:
https://medicine.careers360.com/articles/neet-preparation-tips
Now coming to your question about the fee aspect,
MBBS course fees is different for the government/ government-aided institutions/central universities and private institutions/deemed universities. Depending on the ownership of the college, the MBBS course fee varies.While for government colleges it is less,for private colleges it is more.
For detailed information follow the link below:

Hope this helps.
Good luck.

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