In this scenario, because of being only 20 year old, 2-3 years of bank records and tax returns should be enough, as long as it proves Source of Funds.
Based on your age three years of bank statements and filed taxes should suffice. However, the bank statements should accurately portray the flow of the funds and its source. Please consult an EB-5 attorney to assist you as other financial documentation may be needed to fortify your petition.
2-3 years of business and tax records should be sufficient under this scenario. Further explanation can be provided to inform USCIS why tax and business records prior to this time are not available.