[NH] selling duplex in MA with buyer contingency

We have an offer to sell our duplex in NH, but the buyer has a contingency to close on their property before the sale of our property completes.

The real kicker here is that the buyers property is a commercial property that has been under escrow for several years as part of a large project by the state.

The closing on the sellers property is supposed to close next week. So it seems very close.

The evidence they gave for funds was the P&S of their commercial property plus an e-mail from the attorney about their close date.

The offer is fora little over asking with an inspection/pest inspection contingency.

We are a little antsy because we already had another offer fall through over financing.

What else should we look for/ask for before we sign?