There's no visible difference between the 60D/7D/5D2/5D3 in post processed 24" landscape prints through ISO 800. It's only at higher ISOs that the FF bodies distinguish themselves. Occasionally I've seen a small but insignificant difference at 30". 30", btw, is about the limit for these cameras for critically reviewed landscape prints.
People love to claim there's a huge difference between the formats, but then utterly fail to identify unlabeled prints and 100% screen crops. Even more telling, you can show reversed labels and get people to brag about how much better the 7D images are when they believe the images came from FF!
As for landscape lenses, the same IQ is available cheaper on crop if you will not be using T/S lenses. It's just easier to make UWA and WA glass at a specific quality level for a smaller format. If you will be using T/S lenses, you want FF because there aren't any crop T/S lenses, and the FF lenses are difficult to manipulate with a Canon crop camera's flash housing.
As for going full time pro...the only successful commercial landscape photographers I know are shooting large format film or medium format digital, and their prints easily scale to 6 feet. Also: you can be one of the most talented and visionary landscape photographers in the world and have access to $60k worth of equipment...and still go unnoticed and flat broke. Keep those points in mind while you decide how much money to spend.
I've been saying the same for years... that the benefits of FF compared to APS-C are often WAY over-stated, hypothesized and a result of cognitive dissonance (ie forcing your mind to believe what you want, particularly 'post purchase').
This phenomenom is not just with DSLRs - it's often also the same with food (incl gourmet), drink (including fine wine), vehicles, clothes, etc. While I also do know there are many cases of 'you get what you pay for' - there comes a limit when the 'expensive' is minimally different to the 'extra expensive'.
I've seen many MANY photos from a Canon crop (eg 7D, xxD, xxxD) using EF-S or non-L lenses, and honestly, unless the photos were labelled, viewers (including other pro photographers) could not tell they were not from a FF with an L lens. While I agree there IS some dynamic range and noise advantage to FF... but generally it's not noticable at normal viewing distance to most photos.
Go with what your budget can afford. I find crop sensors particularly good to have a less expensive general purpose, and more portable kit. Yes, I have L glass, and I have used FF. But at this stage I'm very happy with my 7D- and a range of lenses covering 10mm to 300mm.