Can a single player build a clan dojo?

Yes, it possible to do so. Though, it's really not recommended due to the resource costs involved.

To make (or access) the dojo itself, you must first create or join a clan. Then someone needs to make the Clan Key (the blueprint of this will be added to the player's foundry once they join a clan). The resources required are the following:

• 1 Morphic
• 500 Polymer Bundle
• 500 Ferrite
• 1500 Credits
• 12 Hours to build

Afterwards, the basic Clan Dojo, with a basic Clan hall as the starting room, is created. Now, resource costs for building other rooms (connectors, reactors, research facilities, etc.) are scaled depending on what clan size bracket you fall into (in this case, your supposed clan will fall into the Ghost Clan bracket - 1-10 members in total).

Yet still, they are quite expensive for a small number of players to handle, especially due to the usage of "rare" resources at higher levels (such as Forma). Unless you have a large stockpile of resources and credits, it's suggested to have at least 4-6 members to build a basic dojo with the important facilities. But, it's certainly doable with 1-2 people, though not recommended.

I strongly suggest you pay a visit to the Warframe wiki page on Clan Dojos for more information on each room type's costs, as well as for pre-planning the layout. Remember, you don't want to waste resources destroying and creating more rooms than necessary!

Yes it is definitely possible to do a fully functional and practical Dojo by yourself. The resources can be gathered quite "quickly", quickly in quotes, because research costs 3 days to do so you have three days to smartly farm for the next thing to buy.

For a fully functional, Research-aimed Dojo you need 15 Formae, you don't need to get them straight away, mind you, and I'm sure if you don't want to research specific stuff or want it to be not as pretty as to work as a real home for your future clan you can get less Formae and start away, I'd personally start the build at 2 Formae.

Here is how my Clan looks like, built by one person, farmed by one person and started around 75% of the research also by one person:

You start with a clan hall, with 2 doors, this hall is free and requires no forma. The first hallway I start with a Reactor, then I started building all the impractical stuff you don't need to visit or even see to have a functioning Dojo, my goal was the Grandest Clan Hall which gives you 6 free doors and AMPLE space for Trading posts and the 4 useful research centers.

Reactor -- Clan Hall -- Great Clan Hall -- Greater Clan Hall -- (T-Connector leading to an Oracle) -- Grand --(Cross Connector with two reactors) -- Elevator

So basically one long corridor with all the energy needs you have and the Oracle, a thoroughly useless room you need for research. Up until now you have used 10 Formae. The elevator is the starting point for the next bit

Elevator -- Grandest Clan Hall

Now you have 6 free doors, I put all 4 research centers, Tenno Lab, Energy Lab, Bio Lab and Chem Lab on the sides of the Grandest Hall, the front door leads to the elevator and the back door leads to a cross connector, and then an obstacle course and two free nodes. Everything behind the back door is up to you entirely.

Now make Grandest Clan Hall your home and you basically have a massive room with ALL research avaible :D

Very possible. I've built 65 rooms by myself. If you enjoy playing the game and, as mentioned above, use your time wisely between builds it isn't that difficult. Forma will become your biggest nightmare though. Each room requires 1 and it takes ~ 20 minutes for even a chance of getting the blueprint for one. This was basically a majority of my time on warframe, farming forma after forma on void runs.