No. Capital has to be hers and has to be placed at risk in the enterprise, and future instalments under a note are neither yet. Money still in escrow against warranties is in the same position. Only funds actually received, traced and invested can support the petition.
A signed agreement is evidence of a sale, not of available capital
Promoters compress two different ideas into the phrase proof of funds. One is source, meaning the lawful origin of the money, which Solange can establish comfortably from the history of a business she built and sold. The other is path, meaning the documented movement of specific dollars from that origin into the investment.
A vendor take-back note documents an obligation owed to her; it does not document dollars she holds. Three options exist and each has consequences. She can invest only the cash received, if that reaches the applicable amount.
She can wait until enough instalments have been paid, which pushes the timetable and exposes the plan to the statutory adjustment. Or she can borrow against her own assets, in which case the borrowing itself becomes part of the source-and-path analysis and must be secured by assets she owns. Whichever she chooses, the capital must be at risk in the enterprise rather than parked as security.