It does not happen overnight. But what happens is after they take control of the clinic or company they change the sales model to boost reoccurring revenue, this then allows the clinic or target company to take loans out. Because they look good on paper. The company then pays VC back when then pays bank back.
This can be done in about 6mo to 1 year process with some companies. The initial out of pocket expense is small and paid back very quickly.
I also forgot. Sometimes they will take the newly owned company and merge it. During that process they extract more money and load more debt onto the remaining entities, again making the VC money.
In some cases they can even get huge tax benefits by loading the company with debt which offsets the tax bill of the final entity.
When these transactions are done, within the span of a day multiple companies are created and merged and absolved.
There is little to no risk for the VC