Short answer. Yes, if the goods have not been delivered yet. The Civil Code lets a seller totally rescind a sale once the buyer has manifested his inability to perform his obligations, which is a separate ground from an actual breach. Give the buyer notice of your election to rescind, since the statute requires that notice to exercise the right.
What the law says
Where the goods have not been delivered to the buyer, and the buyer has repudiated the contract of sale, or has manifested his inability to perform his obligations thereunder, or has committed a breach thereof, the seller may totally rescind the contract of sale by giving notice of his election so to do to the buyer.
Civil Code, Article 1597 — Seller's Rescission for Buyer's Breach. Read the full provision →
Three separate grounds, not just breach
Article 1597 of the Civil Code gives the seller the right to totally rescind a sale on any of three grounds, where the goods have not yet been delivered to the buyer: the buyer has repudiated the contract, the buyer has manifested his inability to perform his obligations, or the buyer has committed a breach. These are worded as alternatives connected by "or," so a completed breach is only one of the three triggers, not a precondition for the other two. Manifested inability to perform is enough on its own.
Why waiting for an actual default is not required
This matters in exactly the situation you describe: the buyer has not yet missed a payment or otherwise broken the contract, but has clearly shown he cannot come up with the money. Because the statute treats manifested inability to perform as its own independent ground for rescission, you are not required to wait for the buyer to actually default before acting. The clear demonstration of inability is what the law is asking for, not a formal breach that has not yet happened.
The one condition that must still be met
This ground only applies where the goods have not been delivered to the buyer. If delivery already happened, this particular article does not govern rescission on this basis. The statute is specific to the pre-delivery stage of a sale of goods, where the seller still holds the goods and the buyer's failure to be able to perform threatens the seller's expectation of getting paid for them once delivery occurs.
Notice is not optional
The seller does not rescind automatically simply because the buyer's inability becomes apparent. Article 1597 requires the seller to rescind "by giving notice of his election so to do to the buyer." Without that notice, the rescission is not effected under this provision. Giving clear, unambiguous notice of your decision to rescind, rather than simply withholding delivery and staying silent, is what completes the exercise of this right once the buyer's inability to perform has been manifested.