My boyfriend is a patent attorney (you don't want him...based on what you've posted here, you can't afford him). If such an attorney as you do want exists, they are probably a hack. Attorneys are not in the business of marketing, just getting you a patent that you can defend, so would not take a case based on promise of profits (even a good product can be marketed badly). The patentability and marketability of an invention are two completely different things. Litigations might be taken on a contingency basis (i.e., if you have a patent and are suing someone for infringement and a firm thinks there is a good chance of a big payout on the lawsuit), but prosecutions generally are not.