Is it possible to hire a phd student or postdoc by hours?
would it be possible to hire a phd or postdoc by working hours for the projects ?


Yes, but, can you afford one? You've highlighted the cost of a part-time postdoc [at] around 50k annually and noted [you] do not have much money.


  does anyone have rough idea about the price range/hour?


Compute the hourly postdoc rate (from the above salary) and multiply it by some factor (probably greater than two). (The hourly rate is non-trivial to compute, given that many postdocs work more than their contractual hours.)