What is the BEST CRM to use for tracking tenant applications & potential tenants

[Carter McCue]

I am working on scaling my business, and have found that when I have a vacant unit I get a TON of potential tenants calling and emailing me. What is the best way to keep track of them, because even if they do not work for this particular unit, they may work in the future for another unit or even a rent-to-own property. I want to be able to market to them as well, since I have their information.