What is easiest and what makes profit are two different ways of looking at it.
Ultimately you must feel comfortable doing what you do.
What sort of customers do you want?
Low volume high value bespoke work or High volume low price work?
There's a lot of competition with cheap nail bars, where geographically would you position yourself in relation to them to remain competitive and busy?
Before renting space in a shop you could do what the big companies do...a footfall count at peak and off peak times; stand outside and note how many people walk past within 10 mins. Ask yourself are they my customers? How would i get their attention? Will the other staff in a shop mind you sharing 'their customers'?
Renting a space in a shop means considering contractual obligations, many of which (after reading the boards here) are unwritten but expected!
Research as much as possible and be the best at what you do xx