It might be worth finding out where he's up to developmentally if you can, some are walking by 10 months, some are only just crawling. At DC1's 1st birthday party there were some from my NCT group who were walking, some only just bum shuffling.
Baby proof your kitchen/bathroom/life anyway! Get on your hands and knees, look round, what's at your eye level you can see. Remember, a toilet brush is just about the most interesting thing in the world... (second only to the sky remote)
Re the sling, it might also be worth asking if he's been in one before, not all DCs like them by that age, if he's not been in a sling, it might be a waste of money to try to get him in one. (and he'll be heavy, so make sure it's one that spreads the weight well)
Also the bedding, some DCs like sheets and old fashioned bedding, some like sleeping bags, personally I'd go for the bags, but if he's not used to them, it might be a problem. Black out blinds for his room is a very good idea.
Dummies, bottles, sterliser (get a cheap tommy tippy microwave one, you won't be using it for long) formula (find out what he's currently using). Yes, they don't really need formula after 12 months, but I think for 'comfort' it might be worth keeping as much 'normal' as possible.
Have you got a changing bag? (worth spending a bit more, it'll be your handbag for the next 18months after all...) Nappies, wipes, put wipes in every room...
Stair gates (DD was climbing stairs at 11months, a lot can do it before then, either way, you've not got long!)
Buggy wise, I would aim for rear facing, particularly given you're going to want to be making sure you get lots of eye contact and can 'chat' as you're walking along.