Welcome Blue Skies!
If you search around there are actually a hand full of "affiliate WordPress themes" and some are suitable for people promoting a lot of products so I would start there. I've always just used regular themes and tie my links in the content when applicable.
A child theme is always a good idea no matter the site. If you go with Genesis themes they have child themes already setup you can buy.
I'm always hesitant about giving legal advice, especially in other countries since things can vary. I would recommend talking to a professional locally who is well versed in Internet business law so you can help suitable for your unique situation.
This will help you make your PayPal decision https://www.paypal.com/cgi-bin/websc...siness-outside
There are no limits to the number of affiliate programs you can join.