Running a suicide cog normally means you have to re-dish the wheel, it works (I confess to using a bit of Loctite) but it's a bit of a faff.
I can understand not wanting to invest in a proper fixed hub if you're only toying with it, but on the other hand it's easy to sell fixed parts at the moment. Hipsters pay almost new prices for s/h in many cases.
Having a proper hub makes it easier to change cogs etc, you'll experiment with ratios for a bit (don't start to high. try 65 to 69")
If you do start with a suicide cog, probably best to keep both brakes.
Not all my bikes are fixed.