In addition to any application fees, the Planning Board or the Zoning Board of Appeals may, at their discretion, engage the services of planning, engineering, legal, environmental or other professional consultants, at the expense of the applicant, for the review of applications involving significant issues beyond the scope or complexity of normal review. The Planning Board and the Zoning Board of Appeals may require costs to be paid in advance into an escrow account to be held and managed by the City and may deny an application upon failure of the applicant to make such payment in a timely manner. The City Corporation Counsel and the Director of Finance shall establish the terms of the account and shall provide a monthly accounting of the escrow account to the applicant and provisions for further funding of the escrow account when the balance is drawn down to a specified amount.