Hi @Lindsey Clark good luck with your deal!!
I'm a buy and hold investor with 9 doors in Riverside, and without knowing anything else I'd say $215k for a triplex is a sweeeet deal.
Also the current tenants are definitely paying considerably below market. My cheapest apt rents for $750 and my 1-bedrooms are around $1k these days. Sounds like there's a good potential to increase rents, especially with renovations. One thing I will say is the the rental rate you can get in Riverside ranges widely depending on the level of renovation done. For that reason Rent-o-meter is almost useless.
@Jack Bobeck is providing some good information regarding holding costs. Yes your property taxes will likely go up - and I agree - the property taxes are too dang high! However I disagree that your money would be better spent on a flip - renovating a 100-yr-old property from long-distance would be difficult strategy for a newbie - investing on hard mode for sure. Unless you have a background in historic building restoration I wouldn't recommend that.
That being said - definitely get an inspection and try to find an inspector familiar with old buildings. 1920s buildings have different common pitfalls to check than 1950s buildings and 1990s buildings. The most important things to check are things that are more expensive to repair. Other than the foundation; usually the age of the systems - roof, electric, plumbing, and hvac - can tell you if repairs/replacement are needed. I've had to replace the water and drain lines on all my multi-family properties, for example.
Also, separating the meters will be extremely expensive. If you're talking about electric meters that may be worthwhile, but separating water meters probably not. Most of my buildings I pay for water/sewer and include that in the rent.
If there are security deposits, have the seller transfer them directly to the new property mgmt company outside of your closing. If you include them on your HUD (closing disclosure) they can inaccurately be counted as a seller's credit - so keep an eye on that. I made that mistake once.
One aside - this is an off-market deal and there's a realtor involved? Are you paying them out-of-pocket? At a certain point you might consider learning to handle the paperwork yourself. In Florida there are only 2 standard contracts - I'm a licensed realtor but I feel it's fairly straightforward for most deals. You'll need some negotiation ability, and also to be able to communicate your offers clearly to a seller, but I've found it worthwhile to diy in exchange for a price break.