On the job search like everyone else, I found a few locations that say this in their descriptions..."looking for very motivated professional flight instructors with the potential to move into single/multi engine charters". My question is how likley will that happen once I meet FAR minimums? I know this could be a question I can ask the company in person, on the phone etc, but I'm looking for a general idea.

From personal experience, I have seen that companies use the " possibility to move to 135 charter" as a way to lure applicants. Then once you are there, the only time you will see is 172 till the end. Seen this happen to three people in three different states and of course three different companies.

That's about what I figured as well...

I looked into it, the FBO is both a flight school and a charter company.

I'll need to ask more questions but are there any tips or give aways to really determine if they could be luring applicants?

That's sound very familiar, be carefull as posted, they could be luring you.
That is commom practice in this industry.
Also, be aware how many pilots are going to be in front of you for this "135"
Sounds like a scam as always.

Do whatever is best for you as a CFI, and then when you approach 135 mins look for whatever is best for you as a 135 pilot. I wouldn't trust a company that dangles a carrot in front of you like that, and I'm willing to be it also promotes a lot of back stabbing and ass kissing among the CFIs, which would not be very pleasant.

That is a good point above. I will say that I know a lot of people who have been successful at this. Often they are allowed to fly right seat until they get times up but in the mean time they get to fly and log the empty lets. Also, for a lot of operators it is hard to find people knocking on their door with 1200 hours. Not necessarily the case right now but it will be again. A lot of people prefer airlines and can get hired long before they see 1200 hours. Again, not the case right now. How much time do you have?

I would be leery of this myself as I was back in the day. It did work out for me as "they" told you, "they" told me the same. But times are wayyy different now. Sounds like a good barrel of questions to ask in the interview.