The law distinguishes two types of condition. With the condition precedent the effect of the contract begins only on the fulfilment of the condition. Until then the contract is in suspense. If the bank commitment comes, the purchase takes effect. If it fails to arrive within the period, the contract does not take effect and both sides are free.
With the condition subsequent it is the other way round. The contract takes effect immediately but ends if the condition occurs. If the failure of the financing is agreed as a condition subsequent, the purchase applies at first and only falls away once the bank definitively refuses. Until then the buyer is therefore already bound.
For the financing condition, the condition precedent is usually the safer route. As long as the financing is not in place, no full binding arises. Which form fits in the individual case depends on the interests of both sides. The seller often prefers the earliest possible binding, the buyer the latest possible. A balanced clause takes both concerns into account.