After years of doing this part time I am in the process of launching a full time video business.
After expenses of paying crew, rentals, etc. my plan is
1. Pay myself 30%
2. Invest 30% back into my business
3. Save 30% for taxes.
4. Have 10% for misc.
Investing includes marketing, new equipment, trade shows, etc.
I think in a start up business situation you might need to allocate more to marketing.
I would look online for a used arri kit, they are durable.
I just finished the Dave Ramsey class by the way.
JD