If you are staying with APS-C for the foreseeable future keep in mind that the 24-105 becomes a 38-168mm zoom when you multiply by X1.6. The 24-105 is a great lens, but you'll appreciate its qualities more on a FF body.
If you have enjoyed your friend's 16-35, then really consider the equally brilliant EF-S 10-22 or the EF-S 17-55. These will re-sell easily if you move to FF eventually. Like other posters, I'd advise against the L35 simply because of it's limitations on an APS-C body.
Yes to the 17-55 used. If you buy it used, you are basically using it for free until you sell it later for the same price (assuming you don't damage it). 17mm is pretty wide, and the range is useful, and the IQ is great. Wonderful lens.
Also, even if you go full-frame, you might keep a crop body too, just for the free 1.6x telephoto boost it gives you for sports or birds, or whatever.
If/when you go full-frame, buying back the lost 1.6x telephoto length with (good) long glass is insanely expensive.
If for example you have a 70-200 f/2.8, your crop body is giving you 320mm's AND it still at f/2.8. No teleconverter will do that. You lose 1 stop with the 1.4x TC (f/4) and you lose 2 stops (and significant IQ) with the 2x TC.
To get the latest 300mm lens at f/2.8 with a full-frame camera will cost you over $7,000.00, just to get back to (almost) the length you had before at f/2.8. Ouch.