Typically code enforcement will take photos from the roadside or pubic right of way, however there is a procedure in Texas that allows code enforcement to obtain an administrative warrant for code enforcement matters to permit inspections for the purpose of determining the presence of code enforcement violations. So yes, code enforcement can enter your property assuming they obtained the warrant and I have seem where alot of code enforcement officials forget about this.
Repeated citations like you described are somewhat common, I've seen prosecutions of residential property owners for 30 or more code enforcement citations. Sometimes code enforcement just start writing one ticket a week.
You need to work with your code enforcement official, usually you can work with theses guys as long as they see you are making progress, sometimes you can't because you are dealing with someone who enjoys being difficult. It would probably be worth your time and money to locate an attorney in the Dallas area who can represent you to try to negotiate a resolution with the city attorney's office. Failure to address this can cause some dire consequences such as: the city condemning your property if the property is unsafe; ordering the destruction or repair of the property (and claiming a lien upon your property for their expense) [however, the city will be careful in this approach because Dallas got lost a pretty tough case like this a couple of years ago that received alot of attention in the municipal law world], the city can still also prosecute you in municipal court and pursue some pretty steep fines against you due to the condition of the property.
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