I don't mind being paid below market but I definitely need something to make up for this. You could this (following in no particular order): (1) profit sharing (2) equity (3) a higher-than-market level of responsibility for a given experience level and (4) interesting work.
The other thing is that every time I start a new position I'm full of excitement and passion but this excitement drains out of me pretty quickly thanks to terrible decision making by the management, my discovery that I got lowballed on my offer or by others in the team being hired at levels disproportionate to their ability, or by my being forced to work on something completely different from what I promised when I was made the offer, or my discovery that the management are bunch of penny-wise pound-foolish cheapskates.
The TLDR here is that you need to be honest and extremely fair in your dealings. Always ask yourself whether you'd want to continue if you were in the employees position.
Don't ever fall into the trap of thinking that you are doing the employee a favor by giving them a job. Anybody worth hiring can pretty much get an offer with a phone call or two in the current hiring market.