There are many people who make some or all of their income through Permaculture. This would include people who teach it, write about it, are design consultants etc.
I guess what you really want to know is can you make a regular (or better) income from a property using permaculture design? Again, there are individuals & communities around the world who are generating some amount of income from the yields of their property & labour. More so though, they are providing for themselves what they need and selling or otherwise distributing their surplus.
I think 'economic viability' needs to be considered in terms of the sum of the yield which would have to include better health, social culture, quality of life & lifestyle, improved environmental outcomes, species conservation etc as well as the more obvious products of food etc. Sometimes it is the savings made by using a more ecologically sustainable system which encourages less consumption which will make the difference in viability.
Like any business enterprise a permaculture venture needs to be well planned to be viable. But then permaculture is really the way to go about planning. Plan to profit or be economically viable in your venture in the same way you would research & plan any business just base it on the ethics of permaculture: care of Earth, care of people, fair distribution of resources. This would have to conclude that permaculture is economically viable.