I need help in bootstrapping

We have decided to go with LAMP stack based on calibration of our
requirements.I want to know

a) Any issues/challenges/pitfalls you have experienced or we should be
conscious of while implementing based on LAMP.
b) Any alternate architectures you would suggest for us to consider based on
Performance, Cost, Scalability, Talent Pool available ect..

We have also decided to outsource some of our work to an Indian
Startup we are in touch with. I want your suggestions/inputs on

a) Any Criteria we should look at from Talent/Experience/Reference
b) Optimal Rates for Web App and Price Points we can negotiate.
c) Pricing Terms if we want to include Profit-Share options
d) Any risks i should foresee and build clauses for protection.

Please also advice me on any areas we should look at as we build this
application.