They should have no alternative interest than a fiduciary duty (your best interest) to you, especially on your first deal.

Are there any alternative strategies I can use to get a hold of these people?

The idea of tying up $50K for the prospect of earning a net 10% return of $5K isn't an attractive way to build and scale a portfolio.

A sometimes quicker cheaper alternative is the cash for keys approach.

As @Michael Ablan mentioned, depending on your state regs (places where rent increases aren't regulated so heavily) the general rule of thumb that I use when increasing rents is this:1-5% increase: keeps up with inflation and generally not enough to force a tenant to move.6-10% increase: tenants will start to weigh alternatives and will consider moving.

Is their an alternative to sell the ADU by itself?

It seems like a lot of the recommendations for the wording to use on postcards and letters are strongly based around being able to offer cash and close fast. 
Has any one experimented with listing some of the more cr...

The test ad attracted the super riches offering to buy his property instead of the tenancy which kind of freaked him out.

a growing town, growing good jobs attract good tenant types;   dual income young families with a dog. 

The repayment terms for a 401k participant loan are equal monthly/quarterly payments of principal and interest (typically prime plus 1%) over a 5 year term (longer if used to acquire your principal residence).Please note that if you take a full $50,000 and then pay back the loan, you can't take another $50,000 until 12 months after the first loan was fully paid back.Per the loan offset rules that went into effect with the 2018 Tax and Job Act: if you leave your job and the loan is current at the time you leave your job but then the loan goes into default because you left your job, you will have until your tax return deadline (including any timely filed extension) to make the loan current by depositing the outstanding balance into an IRA (and thereby avoid the taxes and penalties that would otherwise apply).Alternative: Rollover Funds to A Solo 401k & Take a 401k loan or Invest in Real Estate DirectlyIf you are self-employed (i.e. active self-employment earned income separate from your w-2 income) with no full-time w-2 employees, you can set up a Solo 401k and then rollover your 401k funds once you leave your current job [NOTE: You generally can't rollover funds that you saved to your current employer plan until you quit.].You could then take a loan of up to 50% of the balance not to exceed $50,000.