In a competitive bidding situation I can see where an offer that includes Unison could put a buyer at a disadvantage just because no one’s ever heard of it.My clients bought a 2 family in Brooklyn.

I’m fairly certain their attorney is their boss, but I don’t want to be at a disadvantage here. 

If you cant qualify for conventional financing and dont have cash you are going to be disadvantaged.

There are some disadvantages with having welfare tenants.1) not all the rent is guaranteed.....tenant portion may be late.2) you will not receive the first rent till after tenant moves in...may take months to get.3) fewer applicants will pass screening criteria.4) if it is a multi unit non welfare tenants may view landlord as slumlord (won't rent).5) Security deposit may be difficult for the tenant to come up with (gov. does not pay)6) frequent inspections usually find petty issues7) frequent ongoing "life issues" for tenants (drinking, stay over guests, relatives etc.) 8) more management intensive9) greater ware and tear on property (not a issue with a C class property)

Just remember to factor in the additional mortgage payment to pay back the line when calculating the cash flow of the potential new property.The one significant disadvantage is that any 2nd position lien can typically be very pricy with HELOCs on the residential side, usually on a variable rate.

I've heard about Delaware LLC series—what are the advantages and disadvantages of using this approach?

This act has been practiced for many years and has some advantages and more not-so-pleasant disadvantages.

I think Mike’s note above is letting you know, you are already at a disadvantage as we see it time-wise, you gotta hit the ground running productively.Seriously, good luck!

Taxes exist no matter what the situation so that isn't a disadvantage.

Now don't get me wrong; portable storage does have some of its disadvantages, too.