Politicians should always “buy votes” by acting in the interest of their constituents. The vote “buying” that should really concern you is called lobbying (see: citizens united), or in some cases outright bribery (see: Justice Thomas; also see: Trump literally selling pardons), or in some cases corruption to point of loss of life (see: the entire Iraq war and surrounding sweatheart contracting deals).
In summary: investing in the future by supporting education: good.Dismantling the EPA for short term political gain at the expense of multiple generations worth of irreparable harm: bad.