It shall be unlawful for any person who is engaged in the business of financing the purchase or sale of motor vehicles or of buying conditional sales contracts, chattel mortgages or leases on motor vehicles sold at retail within this state to accept or receive, or contract or agree to accept or receive, either directly or indirectly, any payment, thing or service of value from any person who is engaged, either directly or indirectly, in the manufacture or wholesale distribution only of motor vehicles, whether patented or unpatented, if the effect of the acceptance or receipt of any such payment, thing or service of value may be to lessen or eliminate competition, or to create or tend to create a monopoly in the person who accepts or receives such payment, thing or service of value, or contracts or agrees to accept or receive the same.