薪水, 工资 ,they are nearly the same,but 薪水 is maybe more in written Chinese seldom,we usually called the 工资 oral or written in Chinese 收入=it includes salary,or the other money ,maybe the investment income or some,if at work,you have no additional income,or maybe the bounus..in Company or in another area 待遇=yeah,just treatment in or work.the vacation,the income,and the whole company will provide you

薪水=工资=收入，u can say:我的薪水/工资/收入是… My salary is… 待遇treatment, the treatment of this work is good.

The difference between them is tiny.

工资=薪水=salary 收入means income,which not only includes salary,but also other benefits such as scholarship,tips and so on. 待遇=the treatment you are enjoying in the company or other institutions.,