What Percent to charge for a renovation project only?

Hi Guys ,I'm doing a side project. (renovation for a client)  

I know what i would make form a house flip but I have no idea what I should be charging on a  renovation for a client .I don't own the property Im just upgrading and modernising the place for a client . New kitchen new floors , new closets , new bathrooms etc 

Should I just charge a percent of the whole job .

Its a high end 80K renovation for a luxury condo  .Is there rule of thumb I can go by ?