What Constitutes Lease Acceptance?

[Art Maydan]

I'm renting out a condo with a lot of interest and the prospects I went with agreed to the terms via email. I sent them the lease and other docs and they didn't reply for 5 hours. It's 3 guys and a broker and they're normally very responsive. I followed up and still got no reply. Shortly after, a comparable prospect offered me $100 more bringing it to $3,500 total. I emailed the first people that rent is $3,500 now and they have an hour to reply.

Since I never received a signed contract from them, is it legal to rescind the offer?