do you think mastering HTML and PHP is an absolute necessity for affiliate marketing?
not at all.. you can find all the php codes you would ever need for free online and pretty much anything that you can't see yourself being able to do you can hire somebody else to do it for you on the cheap.. you can also just outright buy LP's for cheap through sites such as the justindupre.com market place.
thanks to platforms like wordpress setting up a website is cake...Honestly I would say that if you want to learn a skill learn Photoshop.. you can make your own kick ass creatives and even build very good looking LP's which can be spliced and converted to HTML in dreamweaver (if you can't afford the adobe suite torrent that shit)
A basic knowledge of HTML is good and at the very least get yourself a copy of a PHP redirect script (which you can find on several of the AM blogs or just google it.)
I think a lot of people use a lack of coding knowledge as an excuse not to get started. Even on the smallest budget you can afford to outsource your programing.