Unless I brought a bigger down payment or got a co-signer.

That is a real issue and a CO monitor is generally required anywhere you have combustion (gas-fired water heaters, furnaces, garages, etc.).

Has anyone entered into a deal with (trusted) partners whereby you will not be on title (nor mortgage) but instead use a co-ownership agreement to indicate ownership along with rules and responsibilities of each party?

In bringing on a co-sponsor what’s the standard split there?

An example might be a co-worker talked to a relative at Thanksgiving dinner who is a house flipper short of time and they could use some help, and you could learn the ropes.Good Luck, Dan Dietz

The PM should be consulting you at every turnover or renewal if you want to increase rents, that should be a co-effort with them consulting you on the market dynamics they are seeing. 

Your business plan (re: additional capital investment) depends on how long you intend to hold.I always suggest that new hotel investors get started with an experienced operator in a co-GP or LP position.

And now it's even worse, because guess what - on every deal there is a co-broker I have to work with and they are often a cause of frustration for me, to be kind.

I advertise on the radio to find some really great leads, glad to do a co-op with you.Charlie 

Having said that, a rental owner might be reluctant to sign a lease with a tenant if they don't feel as though that tenant will be able to honor that lease (ie. pay rent on time, and honor the rules established within the lease).If you have a roommate who has little to no credit, the landlord will probably require a co-signer to vouch for them; i.e. have a parent who has a monthly income 3x that of this roommate's share of the rent.