§ 40. Collection of taxes and assessments shall be enforced by sale.
The collection of every assessment and every tax upon real estate
returned by the receivers of taxes as unpaid, with the interest and
additions, shall be enforced by a sale of the real estate by the county
treasurer, subject to the right as hereinafter provided of the purchaser
or purchasers at such sale to change or convert such sale into a
transfer of the tax lien or the right of the county to collect such
taxes. Such sale shall be held within six months after the return of
unpaid taxes to the county treasurer.