The other answers provide good descriptions of what may be happening with this particular scam. However, I wanted to add an additional answer to specifically address an incorrect (and dangerous) assumption you've made. In your question, you asked,
Is it safe to trust once after receiving a payment? or Do you have any ideas on any problems that might arise on receiving a payment?
And then, in a comment, you said,
if it's a scam, I wouldn't have received payment, but I got it, how would that be possible?
Based on these statements, it seems like you may be assuming that you receiving money means this business operation is legitimate. Many scam victims make the same assumption. People assume that if someone sends them money as part of some deal, then it must be real - because, why would a scammer throw money away? Time and time again, in scam questions on Money.SE, victims say "but I got money, so it must be real." Yet, it's clear that in pretty much all of these cases, it's not real - it's a scam. In other words, many scams do involve the victim actually receiving money.
Scammers like to exploit incorrect assumptions. Scams are built on exploiting incorrect assumptions. If a scammer knows you are liable to assume they are legitimate if "X" happens, then they will do X, as a way of appearing legitimate.
A victim receiving money as part of a scam usually plays out in one of three ways:
- The scammer has some sort of back door method to get the money back. If they've sent it to you electronically or via check, they may be able to reverse or cancel the transaction. So, the money was never really yours!
- A variation on the first bullet, the scammer may have scammed someone else, and may be sending you someone else's money. Scammers often have several scams linked together. They will use these adjacent scams to make your scam seem more legitimate. If they know you'll trust them because they've sent you money, and they've conned a different victim into giving them access to their bank account, they very well could be sending you money from that other victim's account. They get the benefit of looking more legitimate to you, and at no cost to them!
- The scammer may be sending you real, legitimate money that you are able to keep, but they may be using social engineering to talk you into doing something risky or illegal on their behalf. The scammer is willing to pay real money for this! You are left responsible for your actions, at the end of the day.
- The scammer is getting something from you of greater value than the money they gave you. For instance: processor cycles and electricity to run your computer! As explained elsewhere in answers and comments, most people are completely unaware of the power used and costs associated with running a computer. A scammer who is able to peg a CPU in your PC and then pay you a small amount of money is likely causing you to actually lose money!
With a victims who is ignorant to the costs of running a computer, and who has been lulled into complacency by the fact that they're receiving a check every month, scammers have free reign to make the deal work in their favor. If they send you $5, but your power bill went up by $8, you've been scammed! And who would notice that $8 jump in power consumption? Most people probably wouldn't.