Offer for the house is called Purchase and sale agreement. Most conditions are standard and can be found in your real estate agents easy offer program.
There are 3 types of conditions.
First type is not waivable condition that has to be fulfilled before closing, for example seller agrees to leave the house in clean and swept condition on or before the closing of this transaction, or the buyer agrees to pay the further sum of $5000 dollars after removal of all buyers condition.
Then there are buyers conditions that buyer has to agree to and waive by signing a document named waiver, if buyer does not sign the waiver the deal is null and void and the deposit is returned to the buyer and property will be back on the market. Those conditions can include house inspection, financing or in a case of a business verifying the sales and being approved by the landlord or a supplier.
Third set of conditions is for the seller, for example sellers condition to vacate the property if it is rented, or sellers lawyers condition. The deal is firm only when waivable conditions are signed and waived, if there are no waivable conditions that can happen in multiple offer situation than deal is firm as soon as offer is accepted and deposit is forwarded to listing brokerage account.