Collaborating is healthy; no typo
It's somewhat advanced grammar, strange to some, but very correct. A comma for the last clause would be best, though.
Affectionate
This is a good example of the affectionate use of the demonstrative that. While the antecedent is explained before, that is further clarified in the later clause "to have collaborators".
From Explaining variance in writers' use of demonstratives: A corpus study demonstrating the importance of discourse genre:
The idea of proximal demonstratives expressing the (positive) involvement of the writer vs. distal demonstratives expressing the (negative) backside can be found in many proposals...
...or to be associated with affection, interest, and pride, as opposed to contempt, disapproval, dislike, and mental remoteness.
While that article calls them proximal (positive) and distal (negative), my study with Greek refers to the positive as affectionate and the negative as contemptuous.
Example of affectionate use of a demonstrative:
Oh, I love that guy!
Example of contemptuous use of a demonstrative:
Oh, I hate that teacher!
By using the word that, the contempt or affection is emphasized.
That is what I know and use in my own work with writing and my college major, which was ancient Greek being translated into English. I often explain this to many of my ESL students, which I have experience in for 13 years.
As for the phrase in the question, we could rephrase it as such, using punctuation for clarity:
I think that is a healthy thing (to have collaborators).
Equally, we can say:
I think that is a healthy thing.
More importantly, using demonstrative pronouns (this, that, these, those) can indicate affection or contempt, among other things, all depending on the context. In this situation, the writer is talking well (affectionately) of collaboration, so we would not be wrong to say this is an "affectionate use of the demonstrative".
Anaphoric
But, the use of the demonstrative is more than merely for affection. It also refers to much of the previous explanation, being that it is an anaphoric demonstrative (commonly the far demonstrative: that, those), as opposed to cataphoric, referring to something explained later on (more commonly the near demonstrative: this, these).
Rephrased:
I think [all that I just explained] is a healthy thing (to have collaborators).
If we wanted to improve this, we could argue that it is missing a comma to separate that last parenthetical phrase, meaning we could arrive at this:
I think that is a healthy thing, to have collaborators.
Tip for learners
While learning English as a second language, be cautious of the notion that all sentences must fit into common patterns such as "I think it is". That phrase is common, but not always necessary. "I think that is" also can be proper grammar.
In the phrase used, we have proper use of subjects, verbs, and objects. The writer uses "that" as part of either clear writing or good conversation, linking the ideas in the last sentence to other ideas already explained.