How much did the rehab end up costing and how long did it take to complete?

The primary risks at this point would be       1) to your lender, the risk of a margin call.       2) To you; underestimating the true cost of a project and cost overruns      3) To you; legal risk of securities regulations if you partner looses money. 

I had to go that far away due to the insane cost of real estate in Boston, so I fully understand the predicament.

Not sure the cost of this for you but I feel with hot tub and fireplace you already have a lot of warming options and not get much additional revenue.

@Martti Eckert in our opinion, you'll need to be really familiar with construction, including costs, or be able to find somoen on the ground you can REALLY trust (but still verify).

Then there is the time element with holding costs.

A good real estate accountant can save you thousands of dollars by leveraging entity selection and formation, tax deductions, cost segregations, bonus depreciation and tax planning.I recommend finding an accountant who specializes in real estate taxation, business taxation, financial planning and tax planning.You may want to consider working with your accountant remotely to expand your options.I would also recommend looking for a accountant willing to work with you throughout the year.

Are there any rehab costs?

You need to know what things cost.

Vacancy hurts a bit more, but the biggest issue with renting out large homes is turnover cost.