There are a bunch of sites like these. I've had a buddy of mine approach me years ago with a similar online house plan. He was ready to straight out buy one until I explained how ridiculous sky-cranning any house on any random land was. Little else to say but that I gave him custom plans on which he built his own house a few days later.

I think http://www.houseplans.com/ is the most reasonable of these sites... at least it's a good outlet for out of work designers.

What do I think about www.best-un-built.com? I think it’s a damn good idea! 
As I am the founder of BEST(un)BUILT, one can say - no surprise… 

But as a matter of fact I am myself a very motivated, hard-working architect developing the idea for BEST(un)BUILT out of various conditions within the architect’s daily working routine that I believe are not ideal.  
One central topic is the copyright of architecture and another one is the global waste of creativity / time / money / potential when developing a design which remains unbuilt. 
Show me only one architect who does not know this situation!
Austrian architects invest 73 million Euro per year (!) (working time costs) in competitions. Would be interesting to get numbers of other states?  

We understand BEST(un)BUILT as a “second life” for good design – we want to see those designs built and we offer easy and affordable access to excellent architecture. (in Europe the “online channel” for plans is by the way not at all common.) 

As well we present the architects, how they work, what’s their ideas and background of the designs- (eg https://www.youtube.com/watch?v=9sjICNczm_g sorry only in german by now.)
Our site is a gallery for home plans – and our business model works like a gallery concept, means the original architects are participating whenever one of their plan products is sold. So we reach a WIN WIN situation for both – client and architect. 

The mentioned houseplans.com is a completely different business model and for sure represents a completely different position in the understanding of architecture and design. (And I am not sure if you can buy plans any other than PDF format on their website, which I do not quite understand because the client will need editable CAD plans for the construction phase.)

By the way, I would be more than interested, dear Non Sequitur, how it is possible at all to “give to someone custom plans on which one can build his house a few days later..?

We at BEST(un)BUILT think good design needs time – in the case of BEST(un)BUILT this time has already been invested earlier  and we experience  that good design which is well-thought-out  can be easily adapted to a new site. 

We are interested in innovative, young, fresh and motivating concepts worldwide – so perhaps we can as well address to all those architects right now.

BEST(un)BUILT is always in search of new homes, so feel free to contact us.