Believe it or not, about a year or so ago, that amount of effort could be put into things and often times, for the payment methods I was accepting at the time, I could expect 'finex/bitstamp + 30 to sometimes 60% rate and the only issue was a matter of supply to cater to the volume of demand..
As was mentioned above though, with a new seller account, if you also want to make relatively sure that you're not losing coins to scammers, realistically you should expect 5-7% with a lot of competition. Things sure aren't like they used to be back when the amount of $500 Moneypaks you were able to ACCEPT a day (contingent upon your ability to have as many pre-paids as possible that accepted Greendot MP, and more importantly, your withdrawal techniques - getting thousands of dollars off pre-paids without being noticed) decided what you were able to make...and people expected to pay a 25% and up rate if they wanted to use Moneypaks and the rate just went up as the payment method got shadier and shadier until MP pulled the plug on Moneypaks and switched exclusively to register reloads.
Being that localbitcoins.com is a site where reputation means absolutely everything, much like ones ability to locate honest traders etc..in general within this space, you have an uphill journey ahead if you want to turn profit consistently and not worry about just breaking even the way things have been lately. Who knows though, the tides may indeed be changing with the recent upward price trend...
In any regard, remember what I said regarding your rep/rating and keep that in mind when you're dealing with 2 different buyers with no feed-back have initiated trades but aren't now responding, effectively locking your stock of coin into escrow until they decide to return or...not.
Good luck if you decide to persist, do you REALLY have to buy from Coinbase of all companies though?
BTCe cool