There’s no limits to the number of affiliate programs you sign up for so applying for one today will not prevent you from picking another one later on. In fact, being a member of more affiliate programs simply gives you more options in terms of products to promote plus they’re pretty much all free to join. You can always leave a program if it’s not working out for you or there are no products you want to promote.
It’s also important to research their payout structure. Not all payouts are the same and tier affiliate marketing often offer different payouts. Some might pay you on the first offer but pay you nothing on any upsells. Ideally, you should be paid for every transaction. In doing your research, you’ll find out which affiliate payout structures are the most profitable.