I just bought a 1 bedroom (~750sq ft) loft in downtown Chicago. The building is approximately 6 years old so I am assuming the HVAC unit (which is in my condo) is about that old. It currently is working but I have been noticing some humidity. It is humid in Chicago right now but I'm not sure if it's normal to feel "similar" humidity inside. I checked the filter and it appears to be clean. No funny sounds or leaking from the unit. I did have a home inspector check the condo pre-purchase and he found nothing wrong. However, I'm not sure how reliable home inspectors are when it comes to HVAC stuff.

So, I basically want to know if and how often I should have this serviced. I've been reading to get it serviced annually.

Thanks for your help!