What factors do I need to consider before I get an air con installed?

Mika | February 28 2018 | NW1 8YR

I have an old house that is freezing over winter and boiling over summer. I would like to get a small air con unit installed to cool the master bedroom and sitting room. Are there any important factors that I need to consider before having one installed? Do you get domestic versions like in hotels that do cold air and hot air to help solve both my season issues?