If you are asking about how you should make an online wallet, then you don't have the expertise required to make such a wallet and shouldn't be doing it. Are you actually okay with holding the coins of others? If you fail to secure them properly, you will have a lot of angry customers who will try to take legal action against you.
I agree. You can't just hire developers and entrust it to them because you yourself should also know how the system works. If you have no prior knowledge regarding this then you better stop pursuing it. It seems like you are building a particular profitable business but don't know how it will work out so what you are going to do is pay others to do it for you while the ownership is still yours and earn money out of it. In other words, the fund is yours and the labor is for others but take note that in order for your business to succeed you need to know first how it works so you can lead it better and not just nod all the things that the devs you hired said to you.
The point is, know (what will it be and how it works) the business you want to enter.
