Zoltan Lukac 20+ yrs marketing, sales and general management.

Ali M's advise is right on. Given you're a start-up, therefore, an entrepreneur, I add: YOU are the most "affordable marketing expert" your start-up can hire! In addition to that realization:
- How much marketing investment (that includes the overhead) can you afford in your 5-year business plan? Add 10% and go for it.
- Do you have a top marketing strategist on your advisory board? It's likely to be the best value for money you will be able to get.

Jason K's answer hits the nail at every point! Just to add:
- Are you in a growing segment and did you sign up with the right brand and franchisor? If you didn't, don't throw good money after bad money and get out as unscathed as you can and move on. You can't change those factors.
- If you have scale (more than say 10 locations?), use it to your advantage and build the best team you can afford.
- Does your store GM have clear KPI's, among them Transaction (Tx) and Average Guest Check (AGC)?
- Map your 5 minute universe and own it with Local Store Marketing (LSM), not just flyers, but true community engagement.