Is this a realistic bathroom estimate?

[Mitchell Litam]

A couple bigger pockets podcasts say you can pay about $2500 to rehab a bathroom.

What can I estimate for a bathroom rehab? My bathroom is probabaly 9 by 9. very small bathroom from 1907. probabaly needs a new tub, flooring, vanity and paint. 

What can I expect for rehab? 

Also what is the best book to learn rehab costs? 

If I have a general contractor who does all my rehab do I need to learn what rehab costs are?