Local success is a great thing. This means you're past all the initial start up phase and you have figured out your market (at least locally), you have paying customers and you might have even developed a bit of a brand. These are all wonderful things and great foundational assets to build off of. But now you want to grow and for some businesses that means new geographic markets.
If you're looking for outside investment to grow geographic expansion then you need to decide on the right corporate structure to bring in the investment. This generally comes down to either a centralized or a decentralized structure. Centralized simply means everything is rolled into one big basket. The existing established business and the proposed new location expansions are one big investment pot. You have the advantage here of a business with existing cash flows (hopefully positive) that can create the template for future expansion. It also defrays some risk for new investors. This all sounds good but now you're in the position of having to both value your existing business and factoring in the promise of future growth with the challenge of possible failure. You also may have some entanglements in the local business (i.e. its a family business, partners content with being local, etc.).
One potential direction is to decentralize the legal and business structure. In this case you can create a management company that holds key assets like "the brand", intellectual property, computer systems, training centers, customer service, etc. It can also serve as central accounting, central support, etc. Each geographic location is an independent legal company with ties to the management company. In this scenario your initial location becomes a part of the whole but is independent.
The management company collects fees, commissions, etc. from each location. Each location can now have one or more investors and it's a question of the valuation of a piece and not the whole. This can give you more flexibility in how you price each deal. In one central investment round usually everyone gets the same terms. This reduces flexibility. If someone is a stickler for some point or another they are either out of the deal or you need to concede that point to everyone investing. When you are financing distinct companies/locations each deal is separate. This can be a real advantage when local markets are very different in terms of pay scales, rent costs, legal regulation, etc.
If decentralizing your investments sound interesting to you you'll need an attorney familiar with more advanced forms or interrelated corporate structures for help and don't forget to speak to an account about tax implications of the corporate formation. Where you incorporate will make a difference. If this all sounds a little daunting, it really is not. You just need to spend an hour with an attorney familiar with the topic and you'll feel a whole lot more comfortable with the alternatives.