How much additional cost does a California company have to pay for a $100k employee?

As a very rough answer for planning purposes, the HR costs for most white collar workers with modest benefits runs about 20% of nominal salary, so you can use $20K for a $100K per year worker for a rough cut of your budget, business plan, pitch deck, etc.

This includes payroll taxes and basic benefits (worker's comp insurance, health insurance, and so on), and payroll service costs, but does not include things like administrative support, the HR department, occupancy costs, recruiting and retention costs, bonuses, and so on. It also assumes that any paid time off and overtime incorporated into the $100K figure, not paid extra. The "fully loaded" cost is probably closer to the figure Philip Wattis gives, 2X. Consulting companies and some government contractors use a 2.0-2.3X hourly wage as a zero profit starting point, with any profit coming after that.
What is the proper way to use the rowing machine?

The rowing machine can be intimidating, but once you get the hang of it, it's an effective way to spice up your cardio routine. But while the rowing machine, also called an ergometer, is a calorie buster (about 280 calories in 30 minutes for an 130-pound woman) and

If I do only 40-50 push-ups every day, will it help me lose weight?

If you are venturing into  bodyweight training, good for you. It's a very positive step towards getting healthy. As far as just doing push-ups you will be limiting yourself. A much better option would be to perform 10 push-up, 10

What are good workout songs and routines?

FOR THE SONGS PART:The upper part contains my fav.s. Also, I put some INNA in the lists because the songs mostly consist of regular beats and they are fast.Sweedish House Mafia - Don't You Worry ChildExample - Changed the Way You Kiss MeWisin,Jennifer