When you talk about "building a team", do you envisage hiring employees on a salaried basis?
If so, have you done a proper budget and cash-flow forecast? I ask that question because it will inevitably take many weeks or months before you start getting a worthwhile flow of paying work, and several more weeks before the clients pay for that work. Will you have enough funds in hand to pay your team's salaries and employee benefits - not to mention recruitment costs - during that time?
If that's an issue, it would be better if you started out by getting work that you can do on your own, even if that means turning down large jobs or ones that are beyond your competence. That way, you will at least build up a customer base that could eventually generate enough finance to enable you to start hiring employees. It will also help you get valuable experience, both technical and business.
If that doesn't appeal, another option would be to get the work, and then sub-contract it to specialists in the relevant fields. But I suspect that you will end up paying most of your income to the sub-contractors, and spending most of your time in dealing with them.
I hope this helps. Whatever you decide, good luck with your plans.