It'll work. No plugins though. I use it for my personal blog and have since squarespace 5, but I've never tried it for any of my affiliate attempts. It adapts wonderfully for mobile as long as you haven't added a bunch of custom injection code.

If you pay for personal for a year you're looking at like 96$ a year per site plus domain. Personally, I love squarespace for personal use.

Edit: the only thing that I hate is, starting with squarespace 7 they handle images in a blah way where hotlinking is concerned. For example:

Go to my images page, then click Atari which is http://www.ryanmercer.com/atari/
Now click on say the stack of floppy drives, and you get http://www.ryanmercer.com/atari/2015/9/14/21o97152th46e7sa4offhlfntqte1u
Right click and copy image url, http://static1.squarespace.com/static/547254e6e4b00008d79a3ef1/55f6ab40e4b0b65087bf3c34/55f6be4de4b03f54d2703de9/1442233940800/?format=500w
So now if someone hotlinks to an image on your site it's actually going to be pointing back to squarespace's CDN. Annoys me. They claim it's so images load even faster, which they do BUT I regularly post photos to forums and stuff and liked the image link back to my site, now it just links to squarespaces CDN grumble most forums and similar sites also try and tell you the link is an invalid image link because... no image file extension which means I then usually have to either uplaod it to imgr or something or just toss in something like floppy drive stack mage here. Won't be much of an issue for an affiliate blog I imagine but it's the one (and only) thing about squarespace 7 that chaps my ass.