Besides the obvious higher capex percentage I should keep in reserves, what else should I consider?

But it is actually about 1/3rd the real estate taxes (perhaps as little as 1/5th; "percentage of ground floor to entire building", but SF numbers for the floor and building vary), they pay their own maintenance and water/sewer but nothing beyond that.

You should speak with an attorney about drafting up an agreement between the parties involved detailing the profit and equity percentage splits and your accountant will prepare the tax returns accordingly.

Using the percentages from above I think I need to add 5.6% to 6.7% to property management in my calculations.

Based on him putting in $45K and you putting in $80K, the straight percentage would be 36%/64%. 

He's telling you to wait a week because you're going to go look at cars in person, or put your contact info on some website, to "think about it" a week earlier than whatever he tells you (this is 100% true, and as a lender I will not believe you if you tell me otherwise... sorry :P ), and the second you walk onto that car lot a bunch of car salesmen are going to descend upon you, deploying various lines of BS as a pretext to run your credit ("it's a soft pull" or "we just need your SSN to verify you aren't a terrorist, we aren't going to run your credit") and close you on a car that very day, and there is greater than a 0% chance you will believe what they tell you and screw everything up.The rule is that whatever you tell homebuyers not to do, some non-trivial percentage of them are going to push it one notch farther than you tell them.

For example, if you exclusively use one 10' x 15' bedroom (150 sq ft) for your day trading, and the whole house is 2,000 sq ft, then the percentage is 150/2000 = 7.5%. 

And, as much as HOA's can be a pain, they do keep an eye on things so if your tenants are doing something they shouldn't be you will likely find out about it, where in a SFR you may never find out.In general a lot of people don't like HOA's or CC&R's (I get it), or the possibility of unplanned special assessments (I get that too), but a certain percentage of the HOA dues you would have to pay in a SFR anyway (landscaping, painting, repairs and maintenance, insurance for the outside, pool/spa, gates, etc). 

Your rate will probably go up a full percentage point.  

If they have no skin in the game and they aren’t playing a “mentor role” I don’t know if I would give a percentage of the profits.