Credit Score Management

I am a Real Estate Agent and I need someone who repairs credit.

Basically, my mom is going to be looking into buying a house soon. She wants to check her credit score. Which score is the actual one necessary to check? I’ve seen FICO and all types of other general “credit scores” that could be checked.
Which does a mortgage company look for, and just how many different “types” of credit scores are there? I know that a credit score is a summary of the creditworthiness based on one or up to all three of your credit reports. But where is the safest, cheapest and most reliable place to buy a credit score online?

What are the best ways to start a credit repair business?

Its very hard obtaining a excellent honest credit card with high amounts on them. I currently only have a 300 limit. Will a secure credit card help to increase the credit score? Any advice. I’m also not sure if I should pay off the credit cards that expire within the next couple of years from the credit report.

I want to buy a house and my friend was telling me to go through a credit repair agency and they can “hide” things on your report while you are going through the home buying process is it right or just a ripoff