When I read that you found these plants in your new apartments basement I "LOL'ed". If you are trying to protect yourself from potential legal issues by saying you 'found them' rather then growing them, that is an interesting approach. Stranger things have occurred I suppose.
I must commend you as the adoptive father of these orphaned cannabis plants, heres to you! Do you have a light you are using for the plant, HID, CFL? You have to do quite a bit of reading but here is the main things you need to understand and then build a knowledge base around.
Lights (ideally you want 250w+ HID for flowering plants, fluros works well for veg, radiant heat from the bulb must not get so great that it burns the plants or over-elevates the room temps, this can be controlled with air-cooled hoods + ventilation through that hood)
Ventilation (Fresh air exchange/smell, smell is possibly the #1 way to get caught especially in an apartment)
Temperature/Humidity (75 degrees is ideal, humidity to high = mold)
Growing Medium (Soil or Hydro) (This is what the plant is growing in, not just any soil will do, ask first or read up on it, *Grodan Delta what you have now is a volcanic rock that is whipped up into fibers that are then pressed into the cubes you see)
Digital Timer (To control 18/6, and 12/12 time cycles, can go 24/0 during veg, delaying the need for one)
Container Sizes (Dictates how often to water if in soil, among other variables, typically you want 2-3 gallon or 5 gallon pots for flowering MJ plants, the bigger the root system = the bigger the buds)
Fans (To both circulate the air in the room, and to strengthen the stems by simulating low-wind, lowers chance of mold)
pH meter (You must be aware of the pH of the water you are using 6.5-6.8 soil, less for hydro, if you do not know your pH your plants will never thrive if the pH is outside of these parameters)
*Post a picture of your plants, 1' could mean its getting close to being ready for flowering, or that it just had insufficient light and stretched a lot, these are two very different scenarios. If its bushy and short you may not be far from a flowering lighting schedule which would mean you need a digital timer that will put the lights on for 12 hours, and then off for 12 hours. You will have to deal with 'light leak' issues when you enter flowering, that means that for 12 hours when the lights are off you need absolute darkness for the plants, any light can* alter the states of hormones in the plant resulting in a hermaphrodite plant (male and female plant reproductive parts), this should be avoided at all costs as it will seed out your crop and lower your yield dramatically if you get a he-she instead of a true-female.
It is going to come down to a simple choice. Do you want to invest in items that will allow you to cultivate your new found cannabis in a positive and controlled way, and give you the tools to do it again (with clones, a method of taking a cutting from your current plants and growing the same plant again), or just let them go without investing any money in tools and see what happens? A pH meter will run you $40+ dollars, if you do not have an HID light that will cost you a $100+ at least depending on size, digital timer, and other things like nutrients, a CFM blower/carbon filter, soil, and you are looking at least $200+, most likely a bit more. I am not trying to scare you off! Just letting you know what the situation is before you jump into it, things like smell in mid-flower should be anticipated and prepared for especially in an apartment with neighbors in close proximity. The good news is once you absorb those initial sunk-costs and have your tools ready at hand, you are good to go except for future soil and nutrients needs as they pop up, often nutrients lasts several grows.
