Fair Lending would very much be a concern. You would need to do a risk assessment and implement appropriate monitoring and control procedures to manage the risk. Here’s a link to a CFPB Bulletin on indirect lending: https://www.consumerfinance.gov/newsroom/consumer-financial-protection-bureau-to-hold-auto-lenders-accountable-for-illegal-discriminatory-markup/. It would also be a good idea to check with your attorney to determine if there are any state laws you need to consider pertaining to this type of arrangement.
Regarding fees, follow the disclosure requirement in 1026.18. If you’re referring to the FC – if the dealer charges the fee to cash customers and loan customers alike it wouldn’t be included in the FC.