For the money, a Target bike won't give you as much value as a used bike from shop, thrift-store or garage-sale. Find a knowledgeable friend, shop-employee or ex-racer and look at used MTBs or hybrids from those places. You can typically find a 3-5 year-old $1000 bike for less than $150. Will come with much higher-quality components and frame-material than the Target bike. You may need to replace the tyres and chain, but that's not much and it sounds like you'll need to replace the tyres on the Target bike anyway.

Also learn to use a floor-pump and pressure-gauge. Low-pressure is the main cause of flats and tyre-problems in that weight-range. Good luck!