Hi Ted, I would highly recommend reading the Rocket Mass Heater Builders Guide by Erica and Ernie Wisner. There's been years of trial and error done by lots of people, and that book has a lot of distilled wisdom in it as a result.
As you may already know, a lot of the heat provided by a RMH is via conduction and radiation, so unless you are going to be in the basement with the RMH you might not benefit much from running it. You'll want to thermally isolate the mass from a basement slab, which will draw your stored heat down into the earth where you don't get to use it. There is a ratio of feed tube, burn tunnel, and heat riser that provides the most reliable draw, so if you can avoid reducing the heat riser you'll probably get the best results.
This house at Cob Cottage has a RMH in the downstairs living room that has a very low wooden ceiling (floor for the loft above) that I don't think I was able to stand upright in at 6'6" when I was there. They made a heat shield out of metal can lids that was suspended maybe 6-12" below the ceiling, and maybe 2 feet above the barrel. So you can do the same with a normal/full sized barrel, to help deflect heat if your space is large enough. I can't say their working setup means your setup would also work of course.
I totally understand your desire to do something now though. I personally have felt stuck in a setting where I wasn't able to pursue different ideas like permaculture/natural building, so being able to do something to scratch that itch is important. If you don't get to explore those ideas they either frustrate you endlessly or worse, you give up on your hopes and settle for something less happy.
So since you can make something affordably and give it a try first outdoors (always experiment/learn by building outside!!!) to see how it works and learn the odds and ends, then you can look at doing it inside if you can safely and properly vent the exhaust. I highly recommend you try making a simple gazebo-like back yard rain shelter that you can build the RMH under. You can experiment with it until you are happy with the layout and then cob it in if you like, and live with it for a while. Then I would suggest either taking it apart and rebuilding it inside, or if you can get another cheap/free barrel and bricks you can build a second indoors. But be aware if you make your first one indoors in the basement without outstanding ventilation, and it is leaky and you don't have a way to test for exhaust gases other than by smell, that could be risky in my opinion.
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