Also, you may want to consider getting properties that meet your quick and dirty math under contract first and then do your deep dive during your option period.

Have everyone show during that time period.

IRS liens get in line based on time just like any other lien, but an IRS lien has a 120 day right of redemption (and potentially longer in states where redemption periods are longer by state law).

After a tax sale though, the redemption period varies by state; each state often has its statute that defines the amount of time that the defaulter has to redeem the property after the sale.

If the contract was written correctly, you should be in a due diligence period that allows you to back out for any reason or no reason at all. ( this is not legal advice, I am not an attorney) If this is the case then try to re-negotiate the price based on the new findings.

With a 10 day inspection period and my closing dates ranged any where between 15 to 25 days from the day the offer is accepted.  

Any COC's (change of circumstances) allowable after the loan is started, require a re-disclosure and a new waiting period. 

Many times they will have their own Route Service or be able to recommend one.Make a list of your musts and wants and compare the contracts.Normally they want to have a fixed contract for a set period of time to cover their costs as it is an investment for them and a convenience for you.They need to buy the equipment, pay a service tech to install it, cover all costs of service, repair, collection etc and you provide a room and utilities.What if after 6 months you find a better deal or decide to buy your own and tell them to take it out.

There could be super priority liens as mentioned above such as IRS and state which have rights of redemption periods.  

In most states after a certain period you can claim ownership thought "Adverse Possession" Keep in mind it takes 20 years in MD so it may not be a very practical option.