100K approximately $450?
By business i'll assume you mean something profitable.
Go to Flippa put up 50-70 buck for one of those neatly styled sites. Unique theme, aggregated contents.
Put up bid for a video feed site or deals or travel search.
When you have it. Apply for a pay per call network, one of the reputable ones. (Ringpartner/Callmarketing...etc). They are vastly easy to get into, it is still early days for pay per call advertising.
Before you apply however you can go to fiverr to buy Alexa traffic to jump start your score, these networks try to measure traffic by looking at your Alexa score. Lazy? Yes, but apparently they'll run you through Alexa to verify, even Yahoo Advertiser Syndication networks still rely on Alexa, some.
You will still have like $400 remaining, go to adwords buy placements for any of the highest paying offer in your PPcalls account, one successful rehab call could land you between $150-250. So you need less than 6 conversion to even your overall budget which you can nail under 200$ if you get your placement right.
Almost all the Ppcall networks payout Net 14 days, tops. Especially the dedi ones.
Rinse and repeat. By 2 months if you're really smart and quick on your feet, you may be counting up to 2K USD, as profit, not spend for the ad cycle.
Alternatively you could just start Recharge Card business.