My goal is to invest in the tax liens for the interest payed to the lien holder but would also like to buy tax deeds to flip.

I am interested as well...my thought was there were two lien holders?

This could be either cash from their SDIRA or their cash on hand.2) Having a non disqualified person join as a partner who would use a loan of their choosing outside of an IRA to be a 50% stake holder.3) IF I could find someone that would sell on a Land Contract that would not require a 'personal guarantee', could my SDIRA do say a 50% (or less if possible) down payment and have them carry the remainder on the LC?

It further defines some parameters around other lien holders and their role in a superior foreclosure case.

I sent them the county deed holder's page in hopes that public record would be on my side.

If I ran a ferry moving vehicles across a river and had to refit new or rebuilt engines, I'd need to amortize that cost as it extends the useful life of my asset.My example of a furnace filter holder probably was not a good one, if it's a minor cost and the useful life can't really be determined that repair could well be an expense.

Directly paying a lien holder $25K is NOT going to go toward your down payment. 

When I looked up the foreclosure case online, they were actually having the previous foreclosure sale canceled, to refile, since they failed to name a second mortgage holder. 

In most counties (Not Maricopa though) the lien holder is offered the subsequent taxes first. 

After a certain amount of time, the holder of the land lease will have the right to foreclose.