I think that applying the conservative estimates of 50-60% of rents toward expenses as @Jay Hinrichs recommends is a very smart way to secure your investment long term. My hunch is that you may likely be overestimating your expenses considerably for the first few years assuming 50%, but in the long run you'd be happier that you did once the rehabbed property begins to age and experience unexpected issues (i.e. bad tenants, repairs, etc).
Often the pro-forma sheets I've seen from turnkeys will state very low yearly maintenance estimates (~5% of rent) and total expenses may only be 30% since they are newly rehabbed. These assumptions will make the properties look awesome in terms of cash-on-cash return and monthly cash flow. Problem is if you're buying a long term (30 year) investment, I think it'd be wise to at least run the numbers not using the lowest possible expenses (i.e. 1st year after purchase of rehabbed property), but some estimate of what the average expense may be over 30 years. Could this be 30%...maybe. But based on the collective experience of investors here on BP, it certainly seems that people experience closer to 50%.
I grew up in the OC, live in LA now, and I'm also new. So like you I'm interested in out of state and also interested in turnkeys. I think the cons mentioned by @Jon Holdman highlight some my biggest concerns.
As for fees, they are definitely going to vary depending on who you're talking to and what area you're considering. Though I've seen slightly lower PM fees through turnkeys than what you'd get for hiring a PM on your own.