I have a rental property in MD and I live full time in DE, do i have to file MD state tax?

It depends.  Generally speaking, if you have income in Maryland (including rental income), and you are required to file a Federal Return, you are required to file a Maryland nonresident return.  This website has additional information:  http://taxes.marylandtaxes.com/Individual_Taxes/Individual_Tax_Types/Income_Tax/Filing_Information/D... and includes a link for the Nonresident Instruction manual (on pages 4 and 5 of the manual, more information is given on the filing requirements).

However, if your rental produced a loss, the income is not requried to be reported to Maryland.  

If you do need to file a MD return, you will wish to prepare the MD return first in TurboTax.  Delaware will tax the same income but will give you a credit for the tax you must pay to MD on the same income.  Here is an FAQ to assist you with a Nonresident Return:  https://ttlc.intuit.com/replies/3302052

Yes. Per the state of Delaware, you must file a nonresident return if you have any gross income from Delaware sources.

State of Delaware

You must also file a Maryland return. Per the state of Maryland:

If you are a nonresident of Maryland, you are required to file Form 505 (Maryland Nonresident Income Tax Return) and Form 505NR (Maryland Nonresident Income Tax Calculation) if you have income derived from:

• Tangible property, real or personal, permanently located in Maryland;
• A business, trade, profession or occupation carried on in Maryland; or,
• Gambling winnings derived from Maryland sources.

State of Maryland