It depends on the employment contract you are offered. There could be not much catch. It could be a ****ty job or in a crappy area and the only way they can find people to work there is by offering loan forgiveness or sign on bonuses. There could be stipulations, for example you may need to repay the student loan money if you leave the practice before a certain number of years. There may be a lower base salary or worse benefits package. Lots of things to consider.
Anything that's not included in an upfront salary for a specified amount of time and a specified amount of patients means you need to take the time to understand why it's being offered.
Some reasons for loan repayment, signing bonuses, retention bonuses are:
1. The workload is crushingly high (Kaiser Permanente)
2. The base salary is lower than market (VA)
3. The physician retention is poor (Podunk community hospital)
4. The contract is vaguely worded but the salary is offered in a way that at first glance it appears appealing.
Also there are some places I've bumped into where
1. The salary/hourly is stated by not put in the contract
2. The call duties are not specified, but the salary is "good"
3. The place is in the middle of nowhere, but the salary is below market even with loan repayment and paid call
Lets not forget the instances where you're job duties, salary are clearly specified in the contract but the hospital cuts salaries anyway