Floor beam span
probably anywhere for $5 to $10 a foot, depends on your local market .....
As Gary said, you don't want to have any structural damage to your home from the work you do, insurance companies tend NOT to want to pay for them
Joe is spot on with needing to involve a professional engineer, whether you need a permit or not.
And I'll leave you with this thought, if you post long enough, or go to enough sites you'll find someone that will agree with you thoughts (of course you do not know them, or their level or knowledge or experience) and they will say "Go Ahead! That's what I'd do" WOULD YOU????
"You get what you pay for, and sometimes free costs more!"