Check state laws. Some states do have redemption periods. The length of time depends on whether the owner lived in the house with homestead rights.
If you win at auction most title companies will not issue title insurance for 2+ years. There are a few title companies that will issue title insurance. I just had a title policy issued on a tax sale property that was less than 2 years for $1,600 in Texas. Quiet title takes longer and costs more and then you have to apply for title insurance.
Not all liens are wiped out. Medicare liens, as well as State Hospital liens in Texas, are not wiped out. In some cases, Medicare will negotiate.
Pick houses that are up for tax sale and go door knocking. Face to face will get you better results than direct mail. Check tax bill to see who owns the property. You will pay more at an auction because of competition than one on one with the owner.
Depending on the local there maybe utility bills attached to the property that convey with title transfer. The above property I had to pay lawnmower fees recorded as a lien that was not discharged at the sale. But I knew that ahead of time. Go to the courthouse and pull the file for the tax sale and see if all parties that have liens against the property have been legally served about the sale. If not the sale can be voided.