my one bit of advice that hasn't been stated here already would be to consider having an "in the room" pair of shoes, or flip flops or something. This will help eliminate the possibility of bringing things in from the outside. I also ALWAYS change my clothes before venturing into the room, especially if I've been outside or at the grow store...you never know what you might be dragging with you that could ruin months of hard work.
Another thought - is your floor concrete? you said that you wouldn't want to take of fyour shoes because it was cold, but if it's too cold for your feet, it might be too cold for your plants to grow well in. Your root zone should be warm - at least 65 to 70 if not warmer - so if you are growing on concrete throw down some insulation (2" thick maybe) and some plywood to supply the hard surface to grow on. This should help, but just keep that root zone warm or else you'll be disappointed and really wondering why - I had to learn this the hard way.
Last thought - there are cheaper options available other than hydrostores - hardware stores, online, and even normal gardening stores have the same or similar equipment usually much cheaper than a grow supply shop - but you do what ya gotta do. Good luck friend.