This model works best for more singular, static investments such as specialty funds, private equity and the like.IRA Advisor/Facilitator firms typically offer Checkbook IRA and Solo 401(k) plans that put you more directly in control of investments. 

Custodial fees vary, not necessarily in direct correlation to responsiveness or quality of service.A custodial account may be well suited for assets that are relatively singular and static in nature. 

In that case, you may find CashForMyClosing (singular) to not be a suitable lender unless you can get them to give you the time you will need to do the rehab or unless you can find a HML who will lend you enough pre-rehab to pay off CashForMyClosing (essentially, a pre-rehab refi).Again, transactional lenders offer loan terms measured in days, not months or even weeks.

Different custodians have different pricing models, but they basically need to charge for the processing, as opposed to the conventional model where they earn a commission based on the actual investment.The more singular and static an investment is, the more likely it will work well with a 3rd party custodian.  

Others have brought up great points around a singular employer and the associated risks with that.

I want to focus on a singular area and buy within the next 6 months at the latest.

The average year in which the singularity is predicted to occur is 2040. 

I think this comes from their ability to make quick decisions with a singular vision and goal, not their profession. 

It is an interesting, if singular, data point.

A singular hand written letter that you can photocopy should do the trick.