How math ruins plans (two weeks ago)

The other day my dad started talking about a business venture, he was trying to say that it wasn't a good idea, but when he originally mentioned it he said it like it was positive -- so I tried to crunch the numbers with him and it ended up seeming like a raw deal. We discussed some of the factors that come into play, such as opportunity costs, tax breaks and tax disensentives. 

It's 4:30 AM and I am having a hard time justifying the idea of grad school. It's the upfront cost that bothers me. $42,000 for two years tuition, but also an expectation that I won't be able to work full time (and possible even part time during that two years). 

The social work jobs pay roughly equal to teaching jobs without the steps that the unions guarantee. So... Back to non-profit work in which i take payouts while the admin gets bonuses. 

Let's say the whole two years actually costs me 70,000. It's not unreasonable I've heard lots of people have that kind of debt. 

So I know in my last job I was able to save about 5,000 a year... So that's 14 years plus interest. Assume (and I sure do hope that this the case) that I have a family during this time - and it becomes double that. This is 14-25 years of paying  off monthly loans while working jobs that are incredibly difficult. This is 14-25 years without traveling, major purchases etc. 

14-25 years of the stress of obligation. 

I am lucky enough to have some money on the side that might clear this up, but the risk is that I use the money and never earn it back, basically making my kids poorer, making them have to take on the college debt etc.

The positives of the degree:

New area of opportunity/different jobs

Credentials to add to my experience

New area of study/deepening knowledge

Time with likeminded people

Investment in myself as a community member/caregiver

License to practice private counseling (eventually)

Both my parents turn 60 this year. One is struggling financially more than the other despite the fact they have the same degree(also the degree I'd be getting). A lot of the difference comes from family background not choices. 

My mother has turned her degree into a private business, she is very successful. She's been working in the field for decades and didn't start the private practice until halfway, and didn't invest in it fully until less than 10 years ago. 

I assume a lot of her success has been through building the contacts and earning a solid reputation in the field - which takes time. 

I guess what I am wondering is, is this actually a good investment. Or would my time, money and energy be better spent elsewhere? 

And how do I know?