Last year was easy to claim a loss and maximize my tax benefits because I only collected a half month of rent and spent far more than that getting the place going.

Setting the rent, in this case, would be a bit of a challenge, as a fair rent would find some sort of balance between the risk of a loss if the STR experiences low occupancy and the reward of making more profit should the occupancy be high.  

You have a couple of long-term rentals with mortgages, and they already show a net loss with the "slow" depreciation.

If the market bobbles and your ARV you calculated in the beginning isn't possible at the time of sale and there is a loss, they are likely going to be experiencing a percentage of that loss as well. 

My uncle personally has a few cash flowing rentals that at the time of purchase he got at a good price before major market changes, and even through the overall loss of value in his doors they still maintain a higher growth potential just with the cities intense influx of people, organizations, sports teams ETC...Hope that's in some way helpful!

The loss in most of these funnels is rarely on the better lead sources (although there are some bad ones), the loss is usually on the client who buys leads and thinks they will come ready to sell in a phone call.

We are not real estate professionals (tax purposes)This move will generate a large loss for tax purposes - I understand as non Real estate professionals we can only deduct up to a certain amount of losses each year ~3k with carryforward. 

However, I'm thinking of bringing in another developer, and I'm happy to split profits and losses, we would undertake this deal as a joint venture since this project is very essential to me and the developer's experience is invaluable.

I have read many places where people mention the losses need to be generated in the same year as the sale in order to offset the sell, but in other cases they imply that prior year losses can offset both gains and recapture?

@William Yeh   Under non-recourse loans, the guarantor is not generally responsible for losses the lender incurs, unless they commit certain bad acts; such as fraud, waste, damage or destruction, misapplication, misrepresentation, bankruptcy, or environmental contamination.