Contractor asking for advance, for gas, etc

[April Birdsong]

So this is my first rental property in the middle of rehab. I paid 1/2 of negotiated labor up front and have been purchasing/paying for materials myself.  My contractor asked me for an advancement about 2 weeks ago, which I gave a small amount.  I explained that I did not mind him having a draw as long as certain work is completed, etc.  Although, I want to hold out paying for everything until it is finished.  

What have you all done in these situations. He is now starting to complain about gas money and needing to fix tire. I also have purchased some tools that I thought he would have, such as chain saw, tile cutter, etc.   He is doing a good job, but slow. And I need the work finished so that I can get it on market to rent. 

I do have a contract which states 1/2 to begin job and 1/2 on completion of the job.

I would appreciate any thoughts you have on this situation and how you have handled similar issues in the past.

Thank so much 

April