New primary mortgage will be about $2500 a month, old house that I will rent out long term is $1000 a month.

I'm pretty experienced in long term as I have 17 rentals already but I'm preparing an offer on a bigger multi family complex "32 units" so was looking for proper guidance.  

Of the many strategies I've looked into, House-hacking and short-term rentals piqued my interests. 

If that's the case, you should be able to rate/term refinance at ~75% LTV with a DSCR loan, and with some interest-only basis, your payment will go to ~$850 (based on ROUGH pricing TODAY).

My idea to achieve this is to convert the studio into a short-term rental.I’m trying to determine if I’m forcing this deal to work by relying on the short-term rental strategy or if it’s a reasonable approach given the numbers.

If you ever see someone offering terms that are too good to be true, you might as well just post your SS# and banking information on IG.

In my mind sub to is for short term .. long term rentals is very problematic for many reasons. 

Long term, your property is going to up in value; likely way up.

What about rate and term refinancing?

I'd be happy to get you some rough terms to compare to other options that you have, but I also agree with Jay that you should be wary of just selling and loosing that equity that you've built up in the property.