Here is a risk you should consider in any such strategy, IMO: short borrow costs can spike up to astronomical levels, e.g. 400% per year for KBIO during its Martin Shkreli drama last November/December. (My guess is that much of that was being collected by Shkreli himself through one of those "revenue sharing" agreements, but who knows.) Brokers did used to pay out interest on the principal value of the short, but under ZIRP those days are gone, AFIK. At least, no broker I use has paid out anything noticeable like that for years.
You are technically correct, but it is my experience trading through IB that I have to pay to short stocks a lot of the time. I am always paying interest to short stocks overnight. http://ibkb.interactivebrokers.com/node/41
Every stock will have a short "rate." The harder to borrow, the more you will be charged to short the stock. It is specific to the stock. You may be charged as much as 100% just to short a stock or you may be charged nothing. At one time you did receive interest on short stock, but with interest rates so low, I haven't seen this in awhile. This is why you are better off trading option combo's instead of buying the stock outright for hard to borrow stocks. This way you will be able to capture the hard to borrow rate instead of giving it to your broker.
The borrowing cost is determined by the market. Some times for really hot stocks, hard to borrow stocks, it would be more than 200% annual borrowing rate. Most of the times, It could be 1%, 2% any number.