We get some pretty interesting posts nowadays...

It is really hard for me to find good deals locally nowadays.

Second, a cautionary tale: I have owned a 29 unit apartment complex for 9 years, always paying the mortgage faithfully and at a high interest rate (what were current rates at the time) that the lender should be quite happy with nowadays. 

I rent to the contractors you see working on those large erections of steel at a refinery. 

Is it ideal to go with the same lender with whom I have a mortgage already, and try to get another mortgage; or would it be best to go with whomever offers the best rate nowadays?

The folks that could make money nowadays are only those that have repair crews to rehab properties or the bank that supplies the debt.

For Example, nowadays with the COVID-19 Many Syndicates stopped distributions.2.

So to answer your question, with not ocean front, and a minimum of CoC of 20%, I would offer 125k with all those repairs and nowadays for contractors and rehab time costs, and uncertain times with ocean front competition, this is a NO deal for me.

Or, you can use search engines for this, they are nearly as powerful as the MLS nowadays anyway.3 - So if my Realtor isn't for finding deals, what do they do?

AirBnb is good in near-to-center areas, I wouldn't suggest buying in the very center for the high prices in Prague 1.Financing is nowadays more tough, what is interesting is product from one of local banks which lends to new SPVs (can be owned by foreigner) with 3,99%, duration 25 years and 70% LTV.