For what reason did Orochimaru seek out to Train Sasuke ?

On the off chance that you are discovering answers to these questions, My Friend you have gone to the Right Place. 

We help out Naruto Community by answering their questions and now it's your turn. 

First of all, I realize that feeling when you have questions arising while at the same time viewing Naruto and you seek out to discover answers. 

That is Natural and Good that you watch the series with Great interest. 

Presently, Why Orochimaru Trained Sasuke? 

There is something beyond one Reason. 

First Reason 

Orochimaru needed to have Company of clever and Strong Shinobis so nobody could do any sort of mischief to Orochimaru. 

The reason Orochimaru Trained Sasuke was because Sasuke had Great abilities, Kekkei Genkai Mangekyou Sharingan which would in the end develop into Rinnegan. 

Why would that be? 

Orochimaru didn't just need anyone to occupy. 

Orochimaru needed Kekkai Genkai users around him for insurance purpose. 

Second Reason 

Orochimaru's Dream was to get familiar with all Jutsu existing in Naruto Universe. For this he needed to live on longer, so he made sense of an approach to accomplish everlasting status using bodies of different Shinobis. 

Orochimaru Tried to assume control over Itachi's body yet You and I know it's impossible for Orochimaru to beat Itachi. 

When Orochimaru attempted to beat Itachi, he confronted an easy annihilation by him. 

Not having the option to assume control over Itachi's body, Orochimaru made his brain to prepare sasuke and get control over his body when he grows up. 

That is also why Orochimaru gave a Curse Mark to Sasuke during Chunin Exams. 

Uchiha Clan Possessed Sharingan. Itachi's prowess with his Sharingan was outstanding. Orochimaru expected the same from Sasuke. 

The reason Orochimaru Trained Sasuke was because Sasuke had Great Body, Great Kekkei Genkai Eternal Mangekyo Sharingan, Amazing Tai Jutsu. 

He was the Ultimate Shinobi with every Great Quality. Almost No one could beat him. 

He had all the qualities which Orochimaru was searching for. He also had high IQ at a youthful age. 

Possessing Sasuke's body, Orochimaru would acquire the Sharingan Eyes and furthermore increase a youthful body that would permit him to live any longer. 

So what I am trying to say? 

Orochimaru needed to have Sasuke's abilities to become best before he took his body so that he would be prepared to continue with Sasuke's body. 

Sasuke told Naruto, he realized that he himself alone wouldn't have the option to crush Itachi and was alright with Orochimaru taking his body after he vanquished Itachi. 

However, You and I know Sasuke didn't let Orochimaru assume control over his body as a vessel, that would be because Sasuke's vision was something other than only  beating Itachi in Battle.