It’s one thing to make the sales happening, i.e. having something to sell, having customers and so on, but it’s another thing to manage it all properly. If payments are done on spot, there’s no issues really in terms of invoices, however, if you’re using invoices, i.e. your customers can pay at a later date, the question is, what will the “later date” be. 

There’s a really good indication for you if you’re still debating what the common payment term should be. As you know, a business runs around money. One cannot have it too much, and keeping the business running needs funding. Obviously to make sales happening, you have suppliers, who also require you to pay them. The indication for you is their payment terms really.

If you think about it, you purchase goods and resell them (using a simple example here) the next day. Your suppliers want you to pay your debt in 10 days. If you’d now ask your clients to pay in 15 days, you wouldn’t have money to pay your suppliers, would you? So in a nutshell, make sure that the generally speaking your clients are at least obliged to pay you sooner than you’re having your liabilities due to your suppliers.