Have an older home(late 60s). I've been noticing my grass in a very small area, almost a straight line, has been growing suspiciously fast and dark green. My suspicion is a leaking sewer line. but have had no issues with blockages. I know next to nothing about this, i assume i need to get someone out here to check it?

Do you , by chance, have a septic system?

Negative. In Houston

Nothing to add other than I hope it's not orangeburg pipe. If it is, it's lifespan is about up and it may collapse. Interesting you are not having clogging issues though.

Since your house was built in the 60s you might have cast iron piping, which could have burst since those pipes are at the end of their lifespan. You may need to get a Master Plumber out to do a camera inspection (hydrostatic would damage your pipes further possibly). This will cost about $300. I would do that first before anything else.