1000 sq.ft. is a large 1 bed apartment!. A In the Marina you can rent an unfurnished Studio for around 45k a year or Furnished for 50k - 55k a year. Depends on the building, it's location and size. A small Studio will be 350 sq.ft. a large Studio will be 450 sq.ft +.
Many buildings in The Marina area include A/C. DEWA (Electricity and Water) will be around dhs.150-200 a month. You biggest cost will be your Internet/TV package. Expect to pay dhs.600 a month for a decent package.
Allow 5% of the annual rental for Real Estate fee and 5% security deposit.
There is also a 5% Housing Fee that may be added to your DEWA bill and paid monthly by installments.
If you are not going to have a car then aim for one of the buildings next to the Metro Stations.
Single person - allow dhs.300 a week food bill etc.
Taxis are cheap.
Everything else left over - going out!!!
Hope that helps.