Growing a Team can be considered similar to growing a company.
You need to look at culture fit.
You need to look at skills.
You need to look at growth.
What do I mean by all of these?
Plain and simply, you’ve built a culture unto your own team, whatever it is, it is what you’ve built. The questions you ask in interviews should be shaped around the culture of your team so this person knows what they are getting into and you know what you are getting. It’s at this part in the interview that you move more from the questions of skills and capabilities to essentially how they handle themselves in the hardest and best of times. If they are pausing for answers, good, these questions are not meant to be easy, they are meant for pause and thought. If the answers come easy, well, either they know everyone on your team, or they really don’t see the culture of your team as a big issue.
You have four web developers on your team and no back-end experience. Do you really need a fifth web developer? Probably not. I always try to hire for the potential to get there but sometimes you need skills and need them now, if this person can learn new skills now that is great, if not, you still need those skills. Balance is the word here. If I was starting a company I would not hire 4 bookkeepers and make one my blog administrator because they are a really great person? I need someone that understand blogs, how to write, promote, research, etc. Skill fit should compliment your team either by bringing fresh ideas and blood to the team (i.e., knowledge on new web frameworks) or compliment them (okay now we have a back-end guy).
If you are thinking you are going to be in the position you are in forever, scratch that. You are going to leap into something different and the best compliment to a leader of a team when the leap is the team keeps going on without them AND/OR one of the team steps in to fill your shoes. You need to hire for growth, someone that can someday step up and help you out when you need it the most because when the moment strikes, you are not going to see it coming but you will be thankful that this person was there and you hired for what they could do later on.
Just like any company starting out, growing a team, whether established or new, is eerily close to growing a small company.