Can he give me a land contract if he has an outstanding mortage?

If the taxes aren't brought current by the property owner, the owner of the 1% tax lien can file to become a 1% shared owner of the property and will collect if/when the 99% owner ever sells/transfers the property (hypothetically, assuming the property is ever transferred and that it is worth enough to cover the taxes plus interest outstanding at that time). 

I also think its unlikely that the parish will allow a transfer will outstanding tax debt.  

Banks will not give you financing unless you can offer some liquidity to support debt service for x-months w/o cash flow; and more importantly, if you have other mortgages outstanding, you'll have to show that you have EVEN MORE liquidity to support all debt services for x-months.

Note that lenders will look at your outstanding debt and may change their times depending on your liquidity, so your first mortgage may not necessarily have the same financing terms as your 10th. 

If you have outstanding debt on your credit report, getting them removed either through dispute or by paying them off will make your score jump pretty quickly.Moving forward, the most important thing you can do is make sure every payment is made on time.  

Things like too many late pays on the credit report, lacking necessary income, previous evictions, criminal records, outstanding judgements on credit report, too much debt, etc.Lastly, your PM should be actively engaged in protecting your home.

Owner has an outstanding HELOC of 130k against the property.Current rents are 750 for 3 of the units and either 550 or 575 for one of them.

RealtyTrac let's me find those foreclosures, then I use the county site to get exact details such as outstanding loan balance, case status, etc.

Water billing for outstanding water bills.