Buy House with bad credit score 571

Buy House with bad credit score 571
My credit score is 571.  I just ran a report.  I had a revolving credit card account from when I was very young and I paid it off last year.  Is still says I have a balance due/open account, but I have the receipt of where it was paid off and who I talked with.  I hadn’t run a report before and that’s why this when unnotice for so long. 
 
At this point I’m interested in buying a house and I know that a score of 571 is low/poor.  What can I do to improve my credit.  Once the this dispute is settled, will this raise my credit score?  If so, by how much?

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you also must not have any current credit open
get a secured credit card now
then use this dispute form and dispute the acount