Welcome to the money pit!
Don't worry about not having a social group to play with. You can make good acquaintances, if not new friends, through airsoft. I went to the majority of my games without people I met outside of airsoft.
As Shamal said, having suitable eyepro is an absolute must. You can get very afforable eye protection that's suitable for airsoft, just don't be tempted by the cheapest thing you find on eBay that doesn't come from a known brand such as Bolle. In addition to boots with good ankle support, good gloves are a worthwhile investment - being shot in the knuckles with thin or no gloves can be much more painful (not long lasting though) than you might expect.
Rental might seem expensive to start but think of it as an investment in the hobby. If the worst should happen and you decide airsoft isn't for you, rental will likely be a smaller loss than you would experience buying a two-tone, only to find you find yourself struggling to resell it for even close to what you paid.