I think it really depends on what you plan to do. Mine are 2yr 10mo apart so thought for sure I would be fine with just a pram and either sling or DD1 walking but the reality was a little different and I picked up a second hand double pram once DD2 was a couple of months old which got used every day for our park trip. Was also handy for places like the zoo, south bank, general walks and that kind of thing - I don't do shops with kids really lol so that wasn't a concern. We stopped using it when we moved at the start of this year (DD1 was almost 4), so almost a year of use with that age difference and therefore I can imagine even longer if they were closer together.

Second hand is a good option, mine was super cheap so fairly easy to get my worth. Also doesn't hurt to wait and see as you'll probably not be doing too much straight away but whilst two year olds might like to walk for the novelty, they do tire pretty quick plus it does help keep them safe if you're frequenting busy roads and such.