Question good vacuum pump for short path distillation and rotovap

[mycelium]

What is the best pump to buy, to be used both for a short path distillation set up, and for a roto...probably even filtration. I don't want to spend 2 grand on the pump, but it has to do the job, and do it right...
I know some syntheses say to use reduced pressure, but some say to distill under 40mm Hg which is close to a full vacuum and probably not going to happen with a 100$ HVAC pump.
One that comes with a roto , in this picture, uses water in the bottom of the pump to make a vacuum...do you think it will get down to 40mm Hg?
Thank you

 

[mycelium]

Don't want this post to disappear.
Can you tell me what this kind of pump is called, with water down below
And won't cold water make it more vac, in which case it wouldn't do a real vac all the time...
I am going to look at the vacuum guys post...