Damn, I remember this one! I'll look for it!
http://www.mangago.me/read-manga/jyusya_no_heki
Is it this one?
NekoNani and Hakka have the same guess as me. But your details might be mixed up with some other mangas? Because there is a land development contractor thingy, but that's about it from what you put.
Didnt saw there was already an answer '-'
But theres another thing that resembles it cause there is the arranged marriage thing too
Although i dont remember him marrying a woman in the end.
This manga is set in the middle east where the seme is a prince. The uke is a contractor (I think) trying to get the seme to sign a contract letting them build something on his land. the seme says no and takes the uke to be in his harem. the uke is in love with his boss. things happen and the uke's boss break up with him and the seme and him get together. If you need more details let me know but I'm really looking for this manga! Please help!