Русско-англо-русский юридический словарь

A contract, lease, share, or other right is said to be “onerous” when the obligations attaching to it counter-balance or exceed the advantage to be derived from it, either absolutely or with reference to the particular possessor. Sweet. As used in the civil law and in the systems derived from it, (French, Scotch, Spanish, Mexican) the term also means based upon, supported by, or relating to a good and valuable consideration, i.e. one which imposes a burden or charge in return for the benefit conferred. (Black's Law Dictionary)

Another civil law classification relates to the advantage each party expects to receive from the agreement. A contract, such as a sale of goods, in which both parties expect to receive an advantage in exchange for the service or item they provide, is considered onerous. A contract where one party provides an advantage without receiving anything in return, such as a donation, is a gratuitous contract. (Civil Law Contracts by Christopher Meldrum)

The employment relationship is the legal link between employers and employees. It exists when a person performs work or services under certain conditions in return for remuneration. (Official website of the International Labour Organization (www.ilo.org))

Broadly put, a lease agreement is a contract between two parties, the lessor and the lessee. The lessor is the legal owner of the asset, the lessee obtains the right to use the asset in return for rental payments. (Wikipedia)