"I am accessing the data through various API's that I have found
through my research. All of the API's are free to use."
The API's you "found" and are using may be "free" in a monetary sense - i.e., you don't pay for them and they appear to be public information - but those APIs will have a Terms of Service (TOS) attached to the use of the APIs and the data by the company which provides the APIs. A Terms of service (TOS) (Wikipedia) outlines the legal and acceptable use of the API and is a legally binding contract.
Those TOSs may very well restrict the access and end usage of the data, so read the TOS for each API. A TOS is a contract; break the contract - by accessing the data without permission, without a license, by selling the data, or by any other activity expressly restricted - and you open yourself up to possible legal action, which could include copyright and trademark violations, among others. At very least, the companies that run the APIs can deny you access if you break the TOS; at very most, they can sue you.
A company being "publicly traded" doesn't mean all the data about those companies is free and publicly accessible. Some may be; other data is compiled by the company which provides the API, and they can restrict access to that data through their TOS. If certain types of data are indeed factual - facts can't be copyrighted - the TOS may still legally restrict usage, because the company developed and owns the format that the data is presented in and the API the data is accessed by.
It's possible that you could enter into a licensing agreement with the company that provides the API so you can access the data and monetize it, but that's up to the company, you and your lawyer.