How many visits do I have to make to Brazil until I get citizenship? Do I have to renew the residency every 2 years?

Not exactly, the residency is permanent however within the first 3 years there is a revision by the government of your case to check if the investment is still in the country. After that they issue the Residency Card ID which needs to be successively renewed for a new 9 year period while the foreigner remains as an investor. After becoming 60 years old, it will be no longer necessary to renew it. In connection with citizenship it's a different story. You will be eligible for citizenship after legal residency of 1 to 4 years.