Kell,
I agree with Hops.
How will you personally benefit by this new investor? Will you make a bigger salary? Will you be guaranteed a salary and if so, for how long?
Actually, things could be worse with an outside investor because then you'd have to answer to N mom, plus the investor.
I don't see how this investor benefits you.
Any possibility of you buying your mother out on a long term installment basis? ie: over 10 years, you will pay her (using cash generated by the store's profits) X amount of money every year?
An out right sale of the store could cause your mom to pay sizable capital gains on the lump sum profit of the sale (assuming there's a profit on the sale), whereas an installment sale could save her tax because she'd pay the tax in installments.
Can you convince your mom to retire to Arizona, florida (where ever) and have her sell you the store? She probably won't go for this idea, because she never wants to retire, right?
Just thinking.
dazed