Transactional sex

Transactional sex refers to sexual relationships where the giving and/or receiving of gifts, money or other services is an important factor. The participants do not necessarily frame themselves in terms of prostitutes/clients, but often as girlfriends/boyfriends, or sugar babies/sugar daddies. Those offering sex may or may not feel affection for their partners.
Transactional sex is a superset of sex work, in that the exchange of monetary reward for sex includes a broader set of (usually non-marital) obligations that do not necessarily involve a predetermined payment or gift, but where there is a definite motivation to benefit materially from the sexual exchange. 
In sub-Saharan Africa.
The pervasiveness of transactional sex in sub-Saharan Africa, common in non-marital relationships across all income categories, is closely linked to socio-cultural expectations of gender whereby a man is expected to act as a provider to their partners and women expect a compensation for "giving" sex. This results in implicit assumptions of exchange, whereby for example a man might buy a woman a drink and her acceptance implies a willingness to have sex. Transactional sex is also becoming a vehicle for migration in places where younger women have intimate relationships with older men from, for example, Europe or North America.
The general consensus among those studying transactional sex is that it is associated with the combined effects of poverty, the influence of Western consumerism, the differences in economic power between men and women, and the breakdown of traditional African marriage customs involving bridewealth. Some scholars also associate transactional sex with the use of female erotic power and new inter-generational strategies and argue that these are part of a broader moral economy where the money that young women earn from transactional sex is redistributed to kin and peers.
Though these relationships are common in sub-Sahara Africa, they are also increasingly common in other parts of the world, such as Southeast Asia.