I have run/organized several backpacking trips (from sites such as this) for those who would like to get out and spend time with others of mixed knowledge. My experience was that it is difficult to get groups of about 6 or so who would commit, actually show up, and had all the gear they were supposed to have. It was fun, they were all generally pleased where we went. But this was not a living. Most thought it expensive to have to fly in, spend the first/last night at a hotel/motel my house. Trying to get all at a specified point on a specified time was impossible unless you chartered a van. The less experienced clients, the more trouble you can expect.
I thoroughly enjoyed putting the groups together, or dragging a few along with me who wanted to go some place but needed a 'coach'. I met and made some very nice friends either in my groups or activities others put together and I joined in. Not a lot of that going on here, now.
Once you get a year or so of good business, you might be able to catch a sponsor or two that can offset your expenses.
You need an internet presence of awesome proportions with professional graphics, design and presence. The market is, obviously sites very similar to this one and expensive advertisement in outdoor/hiking magazines. The kick back you will get will be from some here who will say they would do it for 'free' or a reduced cost because they can - and they are not making a living at it.
Examples you can use are the many mountaineering (e.g., Rainier) and trail packing (horse/mule) companies. The latter are pricing themselves out of the market because of costs of maintaining stock. EU and UK have some good examples of what you are trying to do. Different market. They don't have the ease of access to wilderness and open use of National Parks USA has. So people are used to hiring guides. Here there is a lot of 'free' competition and the ability to just go out and 'do it'.
REI and other camping outfitters and the Sierra Club stage training camp outs as well as longer adventures. You could use their pricing as a guide.
You need to specifically identify your market/audience, prepare trips that support those into the areas you are familiar with. Use loads of pictures of where you are going and what the treasures are along the way. Identify a list of all of the positives (some you mentioned above).
Living in Portland is not a big a disadvantage as is the time the 'paying' job is taking away from your possible guided trips.
Alaska has many guide services that provides the kayak and water transportation to spend several days surrounded by glaciers or has an air service to get you some place, drop you off and pick you up later. You can look at those as what they have as a business process including pricing and description of products.
You need links to maps that cover the area that your trip will cover and a tempting need to be there.
mapper.acme.com/?ll=37.31420,-118.77337&z=13
You will need some kind of affordable insurance and an iron clad contract/agreement.
You might consider a marketing/distribution company that has done and can do the administrative busy work that you are trying to get away from.
Perhaps you can broaden your offering by including Sierra in California and Rocky Mountains in Colorado, Wyoming in addition to your home base. It is easy to load up a couple of large duffle bags, toss them on an airline to go someplace. Your clients will anyway. REI, for one can support you from Reno/SF/LA for Sierra and Denver/Cheyenne (Rockies) for extra equipment that you provide to clients.
As another has said, expertise in an associated skill such photography, area geology and history can go a long way to be THE guide they would want to go with.
There are probably many reasons why the market is not saturated with guided tours.
Thanks for asking!!
