Reasonable estimate for a total accessible bathroom renovation?

Be careful with the timing of your payments ! Get it in writing ! You can agree to pay for materials while he is doing this project, or you could also pay the portions of labour that have been completed so far, like half done, half paid, but don't pay the labour for the whole project until it is done.

I've seen too many cases where the guy gets the money and never comes back, or does shoddy workmanship. Even with good intentions, there just naturally is less motivation to do a good job if its already paid. Make sure everything is done right and works properly before you finish paying for the whole project.

I would also recommend getting a walk-in / sit-in tub that can be used as a shower too. When he has a hard time standing up for a shower, he could sit down safely and comfortably inside that thing and enjoy soaking in a very warm tub, and get clean where its hard to reach.

http://www.seabridgebathing.com/ is one example, although there may be different brands and different models and different sizes and various dealers in your area too.

Overall costs can be between $4000 and $7000

Personally, I would not brick in the window Its so nice to have sunlight, If you must, then you can still put in glass blocks with wavy-design or cross-hatch or bubbles or diamond design that let sunlight in but no one can see inside. Also, personally I prefer windows instead of fans, Fans can break down or get noisy and don't clear the air as fast as a window could, but its your decision.

$6500. With all new fixtures.Handicap shower will cost the most because the prep work and moving the plumbing. Then reinforce the shower area for the cement, to form the shower with tiles. Bricking the window area will help the cost also. So you may want to have an extra $500 or so.