First airsoft is not an investment. It is a money pit that keeps getting larger and larger and larger. But that all depends on how serious you are for the sport.
I would say budget yourself 1000$ for everything all said in done.
One primary, secondary and some good equipment to last you many games.
Why I say "good equipment" is because depending on your playing style your gear will take some amount of damage.
Plus if you go with an electric gun, you are going to need a special charger to charge the few batteries you have.
Getting into the sport is something you might want to reconsider if you are tight on money. You could always buy the gun first, but if you don't have the gear you will always not be able to go out and play.
Unless you are buying high end guns like Tokyo Marui and up, don't expect any of the cheaper AEGs to hold its value.