I sent you a direct message.

How you deliver the message would depend on your current relationship, I'd recommend just delivering a letter to them or their mailbox.  

I will message him thank you for the recommendation 

Feel free to message me and let’s connect off-line.

I would like to be able to respond to messages, schedule tours, etc, within the source site to keep it contained, not via text/email.

@Robert Ellis I will message you, thanks 

I will send you a message with my email and information

Feel free to message me.

If you are going to mail, you have to be ready to dish deals that you don't want to someone else.The most important thing if you do decide to mail (I wouldn't based on what you are looking for, everyone is mailing that), is your message.

IG is prob the most relevant social media platform with a decent messaging capabilities.