I am working a website where some people pay money for things that we sell and some people get money for services that they provide to us. Basically, from what others pay us, we pay others.
My question is, how can I estimate if our commisions are OK in order to make profit?
The plan is to have a PayPal service where people can pay (I know that PayPal has some comissions but I don't know if I'm aware of all especially because people from different countries can pay). That there is the problem of sending money to people which might again involve some comision because they might be in other countries.
Is there a formula for calculating this? What (hidden) factors should we take into account in order to get a realistic estimate of how much we can earn in different scenarios?
*Later edit: One extra questions: what costs should be taken into account when dealing with international sales and payments and what is a cheap way of doign this?