Affiliates bottom line is making sure the monthly income is consistent and that payment is made on time. While I do not believe contracts are necessary, I do believe that you should keep all emails and correspondence confirming both the advertising campaign whether it be receiving revenue share, CPC, CPD or CPM income. Once this is done, make sure the advertiser is paying you the quickest way possible which is PayPal and give them your account number so they don't have to chase you for it. Always make sure that the advertiser has your payment details at the beginning so there is no excuse for timely monthly payments into your account. Babylon Affiliate
I wouldn't recommend receiving payment via Paypal - why not simply get paid direct into your own bank account - that's surely the easiest way and also the way that most of the big players operate.