Partner with a friend who is non technical

Try to be honest with yourself: If he wasn't a friend, a stranger whose resume you just received, would you hire him based on his skills alone?

if the answer is still yes, go ahead. If however the answer is no, don't hire him. If he is not a star performer, and startups benefit from star performers especially at the early stage, he will try to use your friendship as shield for staying on the job. I've seen this happen before. You don't want to be in that position.

Sometimes friends and business just don't mix. The only example I personally encountered of "friends starting a business" that actually works is because those friends are stars in different fields. My wife works for a startup with four friend-founders: A genius salesperson, A marketing Guru, A technical power-house and a CEO whose a manager by trade with all the credentials, smooth talking and track record experience to open the wallets of investors. Perfect mix. None of the founders is there just cause he/she is a "friend" to the group. Their friendship is secondary in the matter of constructing their company, which by the way is already successful and approaching $100M in annual revenue.

For tech start-ups sales skills are probably the last skill set you want to be looking for in my opinion but this open to debate.

You need to look a little deeper into his skill set, what can this person do for you that you can't or could have problems doing now & in the future.

The most critical question you need to ask yourself is where does this person add value?

For example, if he has sales skills then naturally he will be able to communicate with people well and will probably be the person you would feel most comfortable pitching your idea to investors?

Could you be more precise when you mean on board though, is this for an equity stake or just to be involved in the project?

Having founded a company with two close friends, I can assure you that there is some value to having people on board that you really trust. Skills can be learned, and if your friend has the right attitude I'm sure they'll learn what they need. I do agree with the others that the friend needs to bring something of value to the table. Like Ron said, you can't bring the friend on board just because they're your friend. That will likely breed resentment long-term. Also, your friend probably won't merit an equal share of the company if those skills aren't present. And make sure he's a doer, not a talker. That's been the biggest issue I've had with friends that have no technical skills but can sell. They just talk about it and never actually do anything.