There could be all sorts of reasons why a client might ask you to do this but in reality the client would want to check you out first to make sure you're honest and don't swindle them. It is a two-way street. I have done Association Management for over 10 years - managing not-for-profit organisations and I did handle their payments and do all their banking for them. I also signed a contract with each one.

If this is a private individual living in another state, whom you've never met or heard of, and especially if there is no contract in place, then yes, I would be very wary about why they want you to do this. Unless there's a legit reason for them doing payments for their business in another state.

Oh, and with 'cos - I always thought it was slang for because and probably depends on their education and upbringing as to whether they use it or not. I find that a lot of younger people use it too.