I'd be very careful about these coops. These are sold on ebay and other websites and are known for being much smaller than they appear to be in the pictures and of very poor build quality. The general advice is to stay away from them and hire a handyman or out of work contractor to build a coop for you. I've seen some of these in person and can say first hand that I'd never buy one.
I hope people who were commenting looked at the measurements: 2x2 housing (4 sq. ft housing total) and 20 sq. ft run space. It would be fine for a pair...maybe three if you're in a year round warm weather area - but no way I'd attempt 4 birds (that's ONE sq. ft of housing per bird). Something you'll also want to consider is that some folk's silkies do NOT do ramps. Personally, I think if you have them from little chicks, they can learn to (you may have to make a wider ramp for them though)...
At the price they are asking you could build your own. I built my coop for $230. Its solid. Its might not be as pretty as some peoples, but I am not done painting. Its just a super simple design. Took me 3 days to do it. I did it myself. I am sure if I had someone who knew what they were doing it woulda been done in a day, its that simple... But even silkies need space. I have 5, and they are not happy in a small space. Grumble Grumble... lol
Yes, that would be my concern, also. They look like the coops sometimes sold with the brand name "Ware." If you do a search here, you'll find comments with people complaining about how the wood disintegrates in the rain, etc.