1. Players don't age in MLO. They could update player stats with DLC updates however.
2. Play competitions to make the most possible money. If you're around and not using the PS3, set it up to search for Coach mode quick match games, just make sure to set your Game Plan under Tactical so that the CPU makes subs and if you want formation changes.
3. You could potentially make money with transfers by buying someone when they're unpopular and selling when they're popular as the price fluctuates based on that, but it would be far easier to just play matches to earn money.
It's going to take a while to build a decent team. My advice is try to buy within your budget, rather than putting all of your money into one or two players.
When you start, most of your players are about 500,000 euros in value. Try building a team with 1m/1.5m players, then move up to 2m etc.
Finally, you will earn money the quickest if you renew players contracts at 20 or 50 games rather than 10 since it costs less the longer the contract. Try to hold on to players longer than you think as if you are constantly selling and buying new players, you will have a really hard time building up the value of your team.