The less likely you are to win a game, the bigger bankroll you need.
For example, SNGs that pay 1/3 of the participants require less bankroll than MTTs. Double or Nothing SNGs where half the field wins require even less bankroll than regular SNGs
1. Satellites require you to win two tournaments in order to get paid, as you say. This is the biggest factor to consider.
2. Often the satellite pays fewer places than a regular tournament does. For example, you might spend $3 and compete in a field of 60 for two $30 tickets, where a normal MTT with 60 entrants might pay twelve places.
3. Then, if you win a ticket, you might be competing in a tournament that has a higher buy-in than your usual stakes. Those higher buy-ins attract tougher players, making it even more difficult to win.
So you definitely to count satellites as more expensive than their buy-in value for bankroll purposes.
I am not a bankroll expert, but if you are following the rule of keeping 100 buy-ins as your bankroll, I suggest multiplying the buy-in amount by three. So if you are rolled for $3 tournaments, you can play satellites with a buy in of $1 or less.
Alternatively, you can use "extra" money for satellites. Let's say you play $3 MTTs and keep a bankroll of $300, but you have $350 in your account. You could chose to use some of that extra $50 for satellites, instead of withdrawing it, or saving it up for a bankroll that would be suitable for larger tournaments. I use this method myself.