I would buy 2 big controllers. Big enough that you both can work on one, but you have a second controller / laptop, for full flexibility. E.g. Terminal Mix 4 if you are on a budget or VCI 400 for full customizeability.
I would add a small mixer so you can mix the 2 controllers together. This can be any small 200 bucks mini-PA mixer, that you can also use to mix monitors independently if you grow to become a bigger act.
Then for transitioning and jumping around add 2 Midi Fighter Pro’s or even 3Ds and custom map them to the software. You can then map the midi fighter banks to sample shots, drum patterns, loops or hotcues or more decks.
As a 2 men act has to custom map almost everything to blend the styles midi-fighters etc. I would largely recommend VDJ Pro and custom map everything. (Which will get much easier in VDJ 8 later this year.) This way you can get multiple decks, sample decks etc.
Some will tell you to go Ableton, but if you want to include more standard workflows this will be hard. If you decide to go Ableton, just go with launchpads for each DJ and preparation will be a b*** and IMHO the sets will be more preparation than innovation or improvisation.
Excluding laptops you can prolly get away with 1000-1500 bucks if you go for the Terminal Mix 4 + Midi Fighter Option (which IMHO is more versatile than the VCI 400 alone).
This is how I would do it.
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