You should spend between a $1,000 - $2,500 for a well built website, search engine optimized, custom ad copy, with full graphics, ready to send traffic to and make some good conversions.
Yes, you could get away with getting a website for only $99 a month, or even for $300 out the door, but is that really what you want? The amount of time, energy and money you would be wasting with these type of cheap sites will supersede what it will cost you to pay the right people the right amount, one-time.
As for advertising, I would recommend you spend whatever your comfortable with, keeping in mind, you'll get what you pay for. If you spend $100.00 a month on advertising, you shouldn't expect to get more then 1 or maybe 2 jobs a month. You decide what pace you want to grow your business. But advertising online, especially investing in SEO
comes at a high price. Could you do it yourself? Of course you could, but like Superior Restoration said, you don't want to be wasting your precious time learning a new business (marketing). Your good at running your business, and these advertising companies are good at what they do.
My opinion, start off spending $500-$1,000 a month in advertising. Split that budget into a few parts (PPC, Social Media, SEO
& SEM). Consistently stick to that budget for 3 months, then make changes from there. If you'r advertising with the right company, you should be increasing your advertising budget by 30% every quarter, to a point where you feel comfortable.