OK Josh…since you are breaking new ground here, the correct answer is probably, “whatever you decide to charge…”
But seriously, this is probably the wrong group to ask, although many on this forum could proivide you with solid estimates of overall operating expenses. If I were you I would pound some pavement around the greater Bay Area and do some telephoning to Southern CA to see what’s charged for renting aircraft of comparable performance: 210’s, Bonanzas, late-model Mooneys, maybe even twin trainers like Duchess or Seminole. You could probably then add a premium to those rates (10%? 20%?) due to the SR22’s cachet. In addition, I would suggest contacting a couple of the fractional ownership outfits to see what their rates are: the combination of monthly fee and per hour wet rate, number of owners per plane and average yearly hours flown by each plane–most will tell you these things–will give you an idea of what you could reasonably charge.
My seat-of-the-pants guess would be around $175-185/hr wet. I ran the proposed SR22 numbers (as of 8-10 months ago) from the Tradewinds fractional group at RHV and that’s what I came up with for their 150 hr/year share. Whether that’s “fair” or not I haven’t a clue, but that’s what your competition will be. I have priced out a couple of fractional ownership arrangements and if you’re interested contact me off-line.
In the final analysis, if it doesn’t fly enough you’re charging too much, if it flies more than you want or the pool of renters becomes too large, then you’re charging too little. An SR22 for rent will be rather unique, so you’re inventing your own market and will have to evaluate it as it were, “on the fly.”