I generally plan for 5% each Vacancy, CapEx, and Maintenance.

Getting a General Contractor (GC) license can be a smart move, but it depends on your priorities as a flipper.

Generally, grouping allows you to count all your hours collectively toward the 500-hour threshold, simplifying the qualification process for multiple properties.

But, in general, what is an appropriate response time, and are there any red flags here? 

Generally the time horizons are longer and you need deeper pockets.If you have already had some success in SF rehab, moving to apartments is not as different as moving to development.

They will bring in shorter term tenants but the lease is still with the tenant the company just does the scouting etc.. still have to vette the tenant but you know the rent is coming from insurance and the rent for me is double market rates at least and generally 6 months to a year so not a ton of turn over and very good tenants..

While I know people can get information themselves, I don't generally hand over all of my information but at this point, I think you are right.  

What qualifies as a one time expense is generally the underwriter's discretion. 

It's generally a hard no, but there are always exceptions.

Generally I would say short term projects.