Hubspot is free, not the best for real estate, but it's free.

Most brokerages will supply one for free to their agents, at KW they have Command, at Exp they have KVCore, both of which do a very good job.

Let me know if you would like to learn more about the advantages of partnering with either of these fine companies.

I am with Ken Jones on this.  I've created my own system with the tools I already have. 

You've received good answers from AR people

Ken Jones, Commercial Real Estate is a techie who always provides good advice.

Hello Jackie White free CRM can offer limited use.

Ken shared a good suggestion. 

Most brokers, franchises and even lenders offer CRM for real estate agents.
Seems like a good deal, but I advise NEVER using these FREE resources. Brokers DO look at what you are doing even though they say they don't. 
The best part of the broker solution is they often have transaction management which gives them even more micromanagement control.
And when the see you are about to leave, they shut off your access to your own database and parse it to the agents in the office. SO. don't do it.

Hubspot and Sugar and Salesforce are incredibly powerful CRM with very advanced tools. If your vision for your business includes 'Inbound Marketing' (inbound is NOT email blasting) these are the ones to choose.
Of course the FREE version either have limited capabiliy OR limit the record size to 100 or less contacts. Perfect for testing and validation.
If you are looking for the TRADITIONAL CRM the one I recommend is WiseAgent.
Be aware the real cost of a crm is in creating the test concept, testing, validation, configuration, implementation and training. Legacy systems are exception based pushing the learning curve over the horizon. More recent developed CRM will rely on contemporary technology and the training will be linear.
Until you know what you really want a spread sheet will be more than adequate for the first year.

Realty Juggler

Like Ken Jones, Commercial Real Estate stated,  Excel is a great way to get started with your database that you could import to something else if you decide to go with a paid version. I've always been wary about using a database provided by and tied to your brokerage for a number of reasons.