Regulations governing IPOs state that new issues are not marginable for at least 30 days following pricing. Therefore, IPO shares must be paid for using cash or cash available to borrow.
Once pricing and allocation have been completed, you will be able to determine how much cash or cash available is needed to settle the purchase of the new offering. Settlement on a new issue varies by the issuer, but is typically the trade date plus two business days.
Fidelity eligibility rules require $2,000 in any account from which an IPO bid is entered.