I have lived in a rental building for years and I'm a former realtor, so my advice is as follows. Is your intention to be hands on (finding and screening tenants, collecting rent, performing maintenance, paying bills, keeping up to date with state and local laws, resolving tenant disputes, keeping records, etc.) OR is your intention to be hands off (paying a property management company to handle everything.
You need to interview property management companies and ask lots of questions. Ask what services they do, cost of such services, what your responsibilities will be and how much responsibility you want to take on, etc.
Next, find other rental buildings and go to the county tax assessor's office to find out who the owner is. Contact them if they are using a property management service. Ask their opinion of how their management service is performing. Do the same with condominimums. Most condos use a property management service. Speak with the HOA and ask what their opinion is of the service.
An issue for you since you're in CO will be snow removal. I imagine this will be an expense that you need to consider. I'm in the New York City suburbs and here they charge plenty for snow removal because they know landlords will pay high prices to clear out their parking lots.