As the owner of a tax lien certificate, you have a first lien position on the property.This means the property owner cannot sell, refinance, get a second mortgage or home equity loan until you receive the amount you paid to satisfy the back taxes PLUS high interest.
If the property owner fails to pay within the period of time specified by state law (called the redemption period), then you get the property
Once you own the property you can do whatever you like; sell it and pocket the profits, rent it for monthly cash-flow, or move in.