That server will not fit properly in that rack, and you would have to floor mount it for it not to fall of the wall
NO!!! 
That is all wrong about the "floor mount it" part lol there would be no support for the back end of the chassis, that is a patch panel rack (more or less).
I worked at Softlayer for some time and all they run is Supermicro servers, Supermicro 3U server chassis would need rails due to the weight of the chassis let a lone the drives and MOBO, or you could get away with a 2-post server rack ( something like this
https://www.racksolutions.com/relay-racks.html ) and some shelves for it but, the rack would need to be mounted down and the server can still slide around...
When picking a rack you should tell this guy to keep this in-mind, will he be adding more to the rack latter and will the rack have networking on it + the rack should ALWAYS support the servers that are going in it.
Here is what I would get or at lest something like this.
Server:Supermicro 3U server chassisHeight: 5.2" (132 mm)
Width: 17.2" (437 mm)
Depth: 25.5" (647 mm)
Gross Weight: 52 lbs (23.59 kg)
Packaging (W x H x L): 26.6" (676 mm) x 13" (330 mm) x 39.9" (1013 mm)http://www.supermicro.com/products/chassis/3U/836/SC836E16-R1200BRackiStarUSA WN1510Weight Capacity: 2200 lbs.
Width: Post-to-post:17.75"::Hole-to-hole:18.5"
Height: 27.25"
Depth: 34.25" maxhttps://www.newegg.com/Product/Product.aspx?Item=N82E16816215213