FarmVille is a great place to go to get away from the 'everyday grind' of life. You can get back to a simpler time and enjoy the peace and tranquility that comes from farming and developing land. However, not everything in FarmVille is an escape from real life. Much like society today, you still need money for just about everything. You have to buy the seeds to plant, and you'll even have to pay for each plot of land you plow.
These costs are easily balanced of course because you're selling your harvested crops for more than it costs to plant them. So making coins is easy, although a little time consuming. Also, there are a lot of other items you can buy in FarmVille to decorate and develop your farm, and you won't be able to invest in these without a nice chunk of change. Buying these things will also get you some experience points, to help you advance to the next level, so you'll have to find a way to make sure you have enough money for all the things you want to buy.
I do have to warn you though, you need to be sure and monitor the amount of money you spend. You may be able to buy that HUGE mansion right now, but you don't want to buy something HUGE, and then have to turn around and sell it because you don't have the money to plant more crops. What I do, is plant my crops first, and THEN buy my big ticket items, that way I have enough coins.