subcontracting

Q: Is it ok for a computer programmer to work for companies like Visa, Master card, American express as a subcontractor? These companies are working to make transactions only.

Q: My friends and I are planning to register a company which focuses on construction solutions. Presently, we are working in a company as employees and all of us are working in different sectors. Our employer has several businesses, and healthcare is one of them. For each machine installation, they hire a third party for construction and finishing works. My question is that we are the employees of the same company and now we want to open our own company to be the third party for their construction work. Can we take orders for construction jobs from our company without showing them that we own the third company? Will this be permissible?