Section 1425. Imposition of tax

Notwithstanding any other provisions of law
  to   the  contrary,  the  county  of  Erie,  acting  through  its  local
  legislative body, is hereby authorized and empowered to adopt and  amend
  local  laws  imposing  in  such  county a tax on each conveyance of real
  property or interest therein when the consideration exceeds five hundred
  dollars, at the rate of two  dollars  and  fifty  cents  for  each  five
  hundred dollars or fractional part thereof; provided, however, that with
  respect  to  (A) a conveyance of a one, two or three-family house and an
  individual residential condominium unit, or interests therein;  and  (B)
  conveyances  where  the consideration is less than five hundred thousand
  dollars, the consideration for the interest conveyed shall  exclude  the
  value  of  any  lien  or  encumbrance  remaining  thereon at the time of
  conveyance. Such local law shall apply to any conveyance occurring on or
  after June first, nineteen  hundred  ninety,  but  shall  not  apply  to
  conveyances  made  on  or  after  such  date pursuant to binding written
  contracts entered into prior to such date, provided  that  the  date  of
  execution  of such contract is confirmed by independent evidence such as
  the recording of the contract, payment of a deposit or other  facts  and
  circumstances as determined by the treasurer.