The paperwork for a Subject To transaction is definitely not something you're going to want to do on your own.

Keep the balloon 10 years + and get a good title company to draft up the paperwork.

Just off the top of my head going out 50 years on a residential loan will result in such a minuscule principal reduction each month that it would be essentially back to the days of interest only loans.  

Essentially the argument is that you are now operating a hotel which requires commercial zoning, compared to the residential zoning that most AirBnB locations have.That being said, I think AirBnB is just starting to scratch the surface of a new industry.  

Few companies offer this (I know of one), but although the criteria and process are similar, it is less paperwork than Homestyle.   

My CPA years ago advised me to file a partnership tax return and attribute the income and expenses to the partnership (so essentially we treat the taxes exactly the same way we would if we had created an LLC and deeded the property over to the LLC).  

Hoping to find some options I called what is to me essentially a hard money broker who I have worked with on almost all of my deals and asked her if she knows people who finance real estate businesses.

Looking for a good book suggestion  to educate myself on the topic of taxes, legal paperwork in real estate, etc.

If it is your primary residence and in your own name you should be able to get very favorable terms on a 30 year fixed rate term which would keep your payments lower than a 20 year term and/or allow you to pull more cash out with a higher LTV.As far as working with the same lender (whether it is conventional mortgage lender or a portfolio lender) would be that you only have to gather all the necessary paperwork once (assuming you do the transaction close to the same time).  

If you make even the smallest mistake in your paperwork, the courts can slam you with triple damages awarded to the tenant.