The time it takes to get an approval of an I-924 petition varies widely from time to time. (USCIS has taken as little as five months in some cases and as long as 10 to 12 months in other cases (where there were no RFEs issued). USCIS is working hard at launching an "expedited" service that will process I-924 applications within 15 days for a premium processing fee. The service was due to be launched in late 2011 although USCIS says they are still working hard on launching it.
If a I-924 application is submitted with a thorough and complete package of documents, organized, collated, structured with colored, labeled tabs, and precise in it's regional economic impact... and with a less than complicated investment structure and business operation, a "typical" time is between four (4) and five (5) months for either a approval or an issuance of RFEs.
When the time comes (most likely within the next 2-3 months) that "premium processing" is implemented by USCIS, that time should drop exponentially to ~15 days, when everything is proper and in order.
If you are curious about the "typical" finder's fee and/or commission, feel free to contact us and we could give you a more complete understanding, as it involves certain SEC regulations and project-specific specifications.