OP said that he does some partial mash brewing already. If you think you are going to someday go to AG, you are going to need a pot that can handle the full-boil volume of your batches. People frequently use 10 gallon pots so they can prevent boilovers (A 5.5 gallon batch will need upwards of 7 gallons pre-boil because of evaporation). I suggested OP look into a keggle, since it can be found relatively cheap, and has the potential for larger batches (I do 10-12 gallon batches in my keggle and split the batches between multiple fermentors. This is also a good opportunity to experiment with different yeasts and/or dry hopping or other post boil additives).
Very good point, a good accurate thermometer is absolutely necessary for making good repeatable all grain batches. I suggest looking into Thermopen, but there are other models that will do the trick.
He said that his basement stays pretty consistent, even during the summer. If you plan on brewing normal ales for the majority of the time, then by all means hold off on a fridge for fermentation control. It seems like OP does understand that yeast health and fermentation control ARE TWO OF THE MOST IMPORTANT THINGS YOU CAN DO TO MAKE GOOD BEER. If he didn’t, theres no excuse now! 
Agreed. But an even bigger waste is spending a couple hundred bucks on a 10 gallon pot, only to realize a couple months down the road you want to do larger batches and realizing you could have had yourself a nice keggle for less than $100 in the first place.
If you decide to go a fridge for fermentation control you absolutely will need some sort of external temperature controller. How many fridges have you seen that let you set the temp to 66F?