Legal Question in Real Estate Law in Illinois

Federal tax liens can indeed affect real estate as do back real estate taxes. If you want to buy the property from him and get "clear title" you will have to deal with these liens. If you just take a deed and give him money you could be really doing yourself a huge disservice. I would recommend first ordering a title insurance commitment to see what shows up as affecting the property. If it's "clear" you may be ok but this is not something I would recommend doing without competent real estate counsel.

If the tax lien was recorded in the county in which the real estate is located, it is a lien on the real estate. You would not be able to sell or mortgage the property until the lien was satisfied, and there is also the possibility that they could foreclose their lien, and you would lose the property.