When I consulted with some folks, most people recommended the need for an incentive to work towards versus a full guarantee.
That is something we have considered doing- increasing the guarantee for all 4 years but less upside.
^^^ this
You might have to lose money, especially the first few years. In which case the partners would have to kick in some dividend to float this new guy (more likely gal). Plus, think about things like maternity leave, etc. It's very possible you won't make the money back for a period of time. BUT, that said, I think if you hire therapists on demand, even if you need to let this person go you'll build equity. But if what you are saying is true, then you CAN definitely afford 200k+ guaranteed first year. This is literally dropping partner K1 in from 500k to 475k (Assuming you have 2. You might have more?) I'm not gonna cry a river for you being cheap here.
You can structure the increased incentive as a loan for buy-in at the end of year 4 for a partnership track. I know a lot of anesthesia/pain and optho practices do this. Very unusual in psych, because practices very small. Assuming you hire a quality person, the loan will be converted to buy-in forgiveness.
I think there are other ways to make this more attractive for mommy track candidates. If you can calculate the per-hour revenue/dividend, you can probably have a tiered partner track and have part-time partners. You can google this--a lot of legal fields are moving in that direction. 500k a year, especially in a lower cost regions mean very little to women. They can't spend that much money. It's useless.
It's not even a student loan issue. It's really a marketing issue: if you are advertising randomly for 150k base nobody will bite--you won't get quality candidates. I'd recommend reaching out directly to fellowships and have a longer discussion with actual high quality potential candidates you like in a fairly detailed way about the ins-and-outs. Typical grads are not really familiar with the business side, and you need to consider this as "mentorship". You have to run the math with the candidate, be like look, we are filling X at X rate with the typical billing rate of whatever for 99213+90833, and the no-show/billing reject rate is whatever, and $X is the excess value for each therapy hour, and expense is Y, so if you fill X slots as a partner you can expect Z. You SHOULD show your corp tax returns. Of course you don't want to just show your panties to any random candidate, hence you want to screen.
In my area, people who run insurance based groups typically hire per hour to start with a very high per hour rate (i.e. typically $250+ per hour), and test the waters with the candidate. Then once it looks more promising they'd discuss bigger commitment. That's also an option for you. It's much easier to get a candidate to fill per hour duties, and in the meanwhile, build up the base to hire more therapists, so if you lose money it won't be a lot and for very long. Facility based per hour jobs can't match this, and you end up getting a really good batch of candidates. Alternatively, some practice basically said that we'll pay you X per visit, but take care all the overhead, and then just let it run for a period of time. They supply the referral source, which is typically the bottleneck. VERY few outright offers a full time job--for exactly the same reason--it's next to impossible to estimate the actual productivity of a particular candidate, and partners don't want to cough up too much dividend to test the waters.